1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546 3547 3548 3549 3550 3551 3552 3553 3554 3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649 3650 3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754 3755 3756 3757 3758 3759 3760 3761 3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831 3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861 3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996 3997 3998 3999 4000 4001 4002 4003 4004 4005 4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083 4084 4085 4086 4087 4088 4089 4090 4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102 4103 4104 4105 4106 4107 4108 4109 4110 4111 4112 4113 4114 4115 4116 4117 4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170 4171 4172 4173 4174 4175 4176 4177 4178 4179 4180 4181 4182 4183 4184 4185 4186 4187 4188 4189 4190 4191 4192 4193 4194 4195 4196 4197 4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208 4209 4210 4211 4212 4213 4214 4215 4216 4217 4218 4219 4220 4221 4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 4256 4257 4258 4259 4260 4261 4262 4263 4264 4265 4266 4267 4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282 4283 4284 4285 4286 4287 4288 4289 4290 4291 4292 4293 4294 4295 4296 4297 4298 4299 4300 4301 4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 4315 4316 4317 4318 4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329 4330 4331 4332 4333 4334 4335 4336 4337 4338 4339 4340 4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371 4372 4373 4374 4375 4376 4377 4378 4379 4380 4381 4382 4383 4384 4385 4386 4387 4388 4389 4390 4391 4392 4393 4394 4395 4396 4397 4398 4399 4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415 4416 4417 4418 4419 4420 4421 4422 4423 4424 4425 4426 4427 4428 4429 4430 4431 4432 4433 4434 4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445 4446 4447 4448 4449 4450 4451 4452 4453 4454 4455 4456 4457 4458 4459 4460 4461 4462 4463 4464 4465 4466 4467 4468 4469 4470 4471 4472 4473 4474 4475 4476 4477 4478 4479 4480 4481 4482 4483 4484 4485 4486 4487 4488 4489 4490 4491 4492 4493 4494 4495 4496 4497 4498 4499 4500 4501 4502 4503 4504 4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517 4518 4519 4520 4521 4522 4523 4524 4525 4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550 4551 4552 4553 4554 4555 4556 4557 4558 4559 4560 4561 4562 4563 4564 4565 4566 4567 4568 4569 4570 4571 4572 4573 4574 4575 4576 4577 4578 4579 4580 4581 4582 4583 4584 4585 4586 4587 4588 4589 4590 4591 4592 4593 4594 4595 4596 4597 4598 4599 4600 4601 4602 4603 4604 4605 4606 4607 4608 4609 4610 4611 4612 4613 4614 4615 4616 4617 4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636 4637 4638 4639 4640 4641 4642 4643 4644 4645 4646 4647 4648 4649 4650 4651 4652 4653 4654 4655 4656 4657 4658 4659 4660 4661 4662 4663 4664 4665 4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680 4681 4682 4683 4684 4685 4686 4687 4688 4689 4690 4691 4692 4693 4694 4695 4696 4697 4698 4699 4700 4701 4702 4703 4704 4705 4706 4707 4708 4709 4710 4711 4712 4713 4714 4715 4716 4717 4718 4719 4720 4721 4722 4723 4724 4725 4726 4727 4728 4729 4730 4731 4732 4733 4734 4735 4736 4737 4738 4739 4740 4741 4742 4743 4744 4745 4746 4747 4748 4749 4750 4751 4752 4753 4754 4755 4756 4757 4758 4759 4760 4761 4762 4763 4764 4765 4766 4767 4768 4769 4770 4771 4772 4773 4774 4775 4776 4777 4778 4779 4780 4781 4782 4783 4784 4785 4786 4787 4788 4789 4790 4791 4792 4793 4794 4795 4796 4797 4798 4799 4800 4801 4802 4803 4804 4805 4806 4807 4808 4809 4810 4811 4812 4813 4814 4815 4816 4817 4818 4819 4820 4821 4822 4823 4824 4825 4826 4827 4828 4829 4830 4831 4832 4833 4834 4835 4836 4837 4838 4839 4840 4841 4842 4843 4844 4845 4846 4847 4848 4849 4850 4851 4852 4853 4854 4855 4856 4857 4858 4859 4860 4861 4862 4863 4864 4865 4866 4867 4868 4869 4870 4871 4872 4873 4874 4875 4876 4877 4878 4879 4880 4881 4882 4883 4884 4885 4886 4887 4888 4889 4890 4891 4892 4893 4894 4895 4896 4897 4898 4899 4900 4901 4902 4903 4904 4905 4906 4907 4908 4909 4910 4911 4912 4913 4914 4915 4916 4917 4918 4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935 4936 4937 4938 4939 4940 4941 4942 4943 4944 4945 4946 4947 4948 4949 4950 4951 4952 4953 4954 4955 4956 4957 4958 4959 4960 4961 4962 4963 4964 4965 4966 4967 4968 4969 4970 4971 4972 4973 4974 4975 4976 4977 4978 4979 4980 4981 4982 4983 4984 4985 4986 4987 4988 4989 4990 4991 4992 4993 4994 4995 4996 4997 4998 4999 5000 5001 5002 5003 5004 5005 5006 5007 5008 5009 5010 5011 5012 5013 5014 5015 5016 5017 5018 5019 5020 5021 5022 5023 5024 5025 5026 5027 5028 5029 5030 5031 5032 5033 5034 5035 5036 5037 5038 5039 5040 5041 5042 5043 5044 5045 5046 5047 5048 5049 5050 5051 5052 5053 5054 5055 5056 5057 5058 5059 5060 5061 5062 5063 5064 5065 5066 5067 5068 5069 5070 5071 5072 5073 5074 5075 5076 5077 5078 5079 5080 5081 5082 5083 5084 5085 5086 5087 5088 5089 5090 5091 5092 5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103 5104 5105 5106 5107 5108 5109 5110 5111 5112 5113 5114 5115 5116 5117 5118 5119 5120 5121 5122 5123 5124 5125 5126 5127 5128 5129 5130 5131 5132 5133 5134 5135 5136 5137 5138 5139 5140 5141 5142 5143 5144 5145 5146 5147 5148 5149 5150 5151 5152 5153 5154 5155 5156 5157 5158 5159 5160 5161 5162 5163 5164 5165 5166 5167 5168 5169 5170 5171 5172 5173 5174 5175 5176 5177 5178 5179 5180 5181 5182 5183 5184 5185 5186 5187 5188 5189 5190 5191 5192 5193 5194 5195 5196 5197 5198 5199 5200 5201 5202 5203 5204 5205 5206 5207 5208 5209 5210 5211 5212 5213 5214 5215 5216 5217 5218 5219 5220 5221 5222 5223 5224 5225 5226 5227 5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238 5239 5240 5241 5242 5243 5244 5245 5246 5247 5248 5249 5250 5251 5252 5253 5254 5255 5256 5257 5258 5259 5260 5261 5262 5263 5264 5265 5266 5267 5268 5269 5270 5271 5272 5273 5274 5275 5276 5277 5278 5279 5280 5281 5282 5283 5284 5285 5286 5287 5288 5289 5290 5291 5292 5293 5294 5295 5296 5297 5298 5299 5300 5301 5302 5303 5304 5305 5306 5307 5308 5309 5310 5311 5312 5313 5314 5315 5316 5317 5318 5319 5320 5321 5322 5323 5324 5325 5326 5327 5328 5329 5330 5331 5332 5333 5334 5335 5336 5337 5338 5339 5340 5341 5342 5343 5344 5345 5346 5347 5348 5349 5350 5351 5352 5353 5354 5355 5356 5357 5358 5359 5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379 5380 5381 5382 5383 5384 5385 5386 5387 5388 5389 5390 5391 5392 5393 5394 5395 5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418 5419 5420 5421 5422 5423 5424 5425 5426 5427 5428 5429 5430 5431 5432 5433 5434 5435 5436 5437 5438 5439 5440 5441 5442 5443 5444 5445 5446 5447 5448 5449 5450 5451 5452 5453 5454 5455 5456 5457 5458 5459 5460 5461 5462 5463 5464 5465 5466 5467 5468 5469 5470 5471 5472 5473 5474 5475 5476 5477 5478 5479 5480 5481 5482 5483 5484 5485 5486 5487 5488 5489 5490 5491 5492 5493 5494 5495 5496 5497 5498 5499 5500 5501 5502 5503 5504 5505 5506 5507 5508 5509 5510 5511 5512 5513 5514 5515 5516 5517 5518 5519 5520 5521 5522 5523 5524 5525 5526 5527 5528 5529 5530 5531 5532 5533 5534 5535 5536 5537 5538 5539 5540 5541 5542 5543 5544 5545 5546 5547 5548 5549 5550 5551 5552 5553 5554 5555 5556 5557 5558 5559 5560 5561 5562 5563 5564 5565 5566 5567 5568 5569 5570 5571 5572 5573 5574 5575 5576 5577 5578 5579 5580 5581 5582 5583 5584 5585 5586 5587 5588 5589 5590 5591 5592 5593 5594 5595 5596 5597 5598 5599 5600 5601 5602 5603 5604 5605 5606 5607 5608 5609 5610 5611 5612 5613 5614 5615 5616 5617 5618 5619 5620 5621 5622 5623 5624 5625 5626 5627 5628 5629 5630 5631 5632 5633 5634 5635 5636 5637 5638 5639 5640 5641 5642 5643 5644 5645 5646 5647 5648 5649 5650 5651 5652 5653 5654 5655 5656 5657 5658 5659 5660 5661 5662 5663 5664 5665 5666 5667 5668 5669 5670 5671 5672 5673 5674 5675 5676 5677 5678 5679 5680 5681 5682 5683 5684 5685 5686 5687 5688 5689 5690 5691 5692 5693 5694 5695 5696 5697 5698 5699 5700 5701 5702 5703 5704 5705 5706 5707 5708 5709 5710 5711 5712 5713 5714 5715 5716 5717 5718 5719 5720 5721 5722 5723 5724 5725 5726 5727 5728 5729 5730 5731 5732 5733 5734 5735 5736 5737 5738 5739 5740 5741 5742 5743 5744 5745 5746 5747 5748 5749 5750 5751 5752 5753 5754 5755 5756 5757 5758 5759 5760 5761 5762 5763 5764 5765 5766 5767 5768 5769 5770 5771 5772 5773 5774 5775 5776 5777 5778 5779 5780 5781 5782 5783 5784 5785 5786 5787 5788 5789 5790 5791 5792 5793 5794 5795 5796 5797 5798 5799 5800 5801 5802 5803 5804 5805 5806 5807 5808 5809 5810 5811 5812 5813 5814 5815 5816 5817 5818 5819 5820 5821 5822 5823 5824 5825 5826 5827 5828 5829 5830 5831 5832 5833 5834 5835 5836 5837 5838 5839 5840 5841 5842 5843 5844 5845 5846 5847 5848 5849 5850 5851 5852 5853 5854 5855 5856 5857 5858 5859 5860 5861 5862 5863 5864 5865 5866 5867 5868 5869 5870 5871 5872 5873 5874 5875 5876 5877 5878 5879 5880 5881 5882 5883 5884 5885 5886 5887 5888 5889 5890 5891 5892 5893 5894 5895 5896 5897 5898 5899 5900 5901 5902 5903 5904 5905 5906 5907 5908 5909 5910 5911 5912 5913 5914 5915 5916 5917 5918 5919 5920 5921 5922 5923 5924 5925 5926 5927 5928 5929 5930 5931 5932 5933 5934 5935 5936 5937 5938 5939 5940 5941 5942 5943 5944 5945 5946 5947 5948 5949 5950 5951 5952 5953 5954 5955 5956 5957 5958 5959 5960 5961 5962 5963 5964 5965 5966 5967 5968 5969 5970 5971 5972 5973 5974 5975 5976 5977 5978 5979 5980 5981 5982 5983 5984 5985 5986 5987 5988 5989 5990 5991 5992 5993 5994 5995 5996 5997 5998 5999 6000 6001 6002 6003 6004 6005 6006 6007 6008 6009 6010 6011 6012 6013 6014 6015 6016 6017 6018 6019 6020 6021 6022 6023 6024 6025 6026 6027 6028 6029 6030 6031 6032 6033 6034 6035 6036 6037 6038 6039 6040 6041 6042 6043 6044 6045 6046 6047 6048 6049 6050 6051 6052 6053 6054 6055 6056 6057 6058 6059 6060 6061 6062 6063 6064 6065 6066 6067 6068 6069 6070 6071 6072 6073 6074 6075 6076 6077 6078 6079 6080 6081 6082 6083 6084 6085 6086 6087 6088 6089 6090 6091 6092 6093 6094 6095 6096 6097 6098 6099 6100 6101 6102 6103 6104 6105 6106 6107 6108 6109 6110 6111 6112 6113 6114 6115 6116 6117 6118 6119 6120 6121 6122 6123 6124 6125 6126 6127 6128 6129 6130 6131 6132 6133 6134 6135 6136 6137 6138 6139 6140 6141 6142 6143 6144 6145 6146 6147 6148 6149 6150 6151 6152 6153 6154 6155 6156 6157 6158 6159 6160 6161 6162 6163 6164 6165 6166 6167 6168 6169 6170 6171 6172 6173 6174 6175 6176 6177 6178 6179 6180 6181 6182 6183 6184 6185 6186 6187 6188 6189 6190 6191 6192 6193 6194 6195 6196 6197 6198 6199 6200 6201 6202 6203 6204 6205 6206 6207 6208 6209 6210 6211 6212 6213 6214 6215 6216 6217 6218 6219 6220 6221 6222 6223 6224 6225 6226 6227 6228 6229 6230 6231 6232 6233 6234 6235 6236 6237 6238 6239 6240 6241 6242 6243 6244 6245 6246 6247 6248 6249 6250 6251 6252 6253 6254 6255 6256 6257 6258 6259 6260 6261 6262 6263 6264 6265 6266 6267 6268 6269 6270 6271 6272 6273 6274 6275 6276 6277 6278 6279 6280 6281 6282 6283 6284 6285 6286 6287 6288 6289 6290 6291 6292 6293 6294 6295 6296 6297 6298 6299 6300 6301 6302 6303 6304 6305 6306 6307 6308 6309 6310 6311 6312 6313 6314 6315 6316 6317 6318 6319 6320 6321 6322 6323 6324 6325 6326 6327 6328 6329 6330 6331 6332 6333 6334 6335 6336 6337 6338 6339 6340 6341 6342 6343 6344 6345 6346 6347 6348 6349 6350 6351 6352 6353 6354 6355 6356 6357 6358 6359 6360 6361 6362 6363 6364 6365 6366 6367 6368 6369 6370 6371 6372 6373 6374 6375 6376 6377 6378 6379 6380 6381 6382 6383 6384 6385 6386 6387 6388 6389 6390 6391 6392 6393 6394 6395 6396 6397 6398 6399 6400 6401 6402 6403 6404 6405 6406 6407 6408 6409 6410 6411 6412 6413 6414 6415 6416 6417 6418 6419 6420 6421 6422 6423 6424 6425 6426 6427 6428 6429 6430 6431 6432 6433 6434 6435 6436 6437 6438 6439 6440 6441 6442 6443 6444 6445 6446 6447 6448 6449 6450 6451 6452 6453 6454 6455 6456 6457 6458 6459 6460 6461 6462 6463 6464 6465 6466 6467 6468 6469 6470 6471 6472 6473 6474 6475 6476 6477 6478 6479 6480 6481 6482 6483 6484 6485 6486 6487 6488 6489 6490 6491 6492 6493 6494 6495 6496 6497 6498 6499 6500 6501 6502 6503 6504 6505 6506 6507 6508 6509 6510 6511 6512 6513 6514 6515 6516 6517 6518 6519 6520 6521 6522 6523 6524 6525 6526 6527 6528 6529 6530 6531 6532 6533 6534 6535 6536 6537 6538 6539 6540 6541 6542 6543 6544 6545 6546 6547 6548 6549 6550 6551 6552 6553 6554 6555 6556 6557 6558 6559 6560 6561 6562 6563 6564 6565 6566 6567 6568 6569 6570 6571 6572 6573 6574 6575 6576 6577 6578 6579 6580 6581 6582 6583 6584 6585 6586 6587 6588 6589 6590 6591 6592 6593 6594 6595 6596 6597 6598 6599 6600 6601 6602 6603 6604 6605 6606 6607 6608 6609 6610 6611 6612 6613 6614 6615 6616 6617 6618 6619 6620 6621 6622 6623 6624 6625 6626 6627 6628 6629 6630 6631 6632 6633 6634 6635 6636 6637 6638 6639 6640 6641 6642 6643 6644 6645 6646 6647 6648 6649 6650 6651 6652 6653 6654 6655 6656 6657 6658 6659 6660 6661 6662 6663 6664 6665 6666 6667 6668 6669 6670 6671 6672 6673 6674 6675 6676 6677 6678 6679 6680 6681 6682 6683 6684 6685 6686 6687 6688 6689 6690 6691 6692 6693 6694 6695 6696 6697 6698 6699 6700 6701 6702 6703 6704 6705 6706 6707 6708 6709 6710 6711 6712 6713 6714 6715 6716 6717 6718 6719 6720 6721 6722 6723 6724 6725 6726 6727 6728 6729 6730 6731 6732 6733 6734 6735 6736 6737 6738 6739 6740 6741 6742 6743 6744 6745 6746 6747 6748 6749 6750 6751 6752 6753 6754 6755 6756 6757 6758 6759 6760 6761 6762 6763 6764 6765 6766 6767 6768 6769 6770 6771 6772 6773 6774 6775 6776 6777 6778 6779 6780 6781 6782 6783 6784 6785 6786 6787 6788 6789 6790 6791 6792 6793 6794 6795 6796 6797 6798 6799 6800 6801 6802 6803 6804 6805 6806 6807 6808 6809 6810 6811 6812 6813 6814 6815 6816 6817 6818 6819 6820 6821 6822 6823 6824 6825 6826 6827 6828 6829 6830 6831 6832 6833 6834 6835 6836 6837 6838 6839 6840 6841 6842 6843 6844 6845 6846 6847 6848 6849 6850 6851 6852 6853 6854 6855 6856 6857 6858 6859 6860 6861 6862 6863 6864 6865 6866 6867 6868 6869 6870 6871 6872 6873 6874 6875 6876 6877 6878 6879 6880 6881 6882 6883 6884 6885 6886 6887 6888 6889 6890 6891 6892 6893 6894 6895 6896 6897 6898 6899 6900 6901 6902 6903 6904 6905 6906 6907 6908 6909 6910 6911 6912 6913 6914 6915 6916 6917 6918 6919 6920 6921 6922 6923 6924 6925 6926 6927 6928 6929 6930 6931 6932 6933 6934 6935 6936 6937 6938 6939 6940 6941 6942 6943 6944 6945 6946 6947 6948 6949 6950 6951 6952 6953 6954 6955 6956 6957 6958 6959 6960 6961 6962 6963 6964 6965 6966 6967 6968 6969 6970 6971 6972 6973 6974 6975 6976 6977 6978 6979 6980 6981 6982 6983 6984 6985 6986 6987 6988 6989 6990 6991 6992 6993 6994 6995 6996 6997 6998 6999 7000 7001 7002 7003 7004 7005 7006 7007 7008 7009 7010 7011 7012 7013 7014 7015 7016 7017 7018 7019 7020 7021 7022 7023 7024 7025 7026 7027 7028 7029 7030 7031 7032 7033 7034 7035 7036 7037 7038 7039 7040 7041 7042 7043 7044 7045 7046 7047
|
@node Evaluation and Compilation, Types and Classes, Syntax, Top
@chapter Evaluation and Compilation
@menu
* Evaluation::
* Compilation::
* Declarations::
* Lambda Lists::
* Error Checking in Function Calls::
* Traversal Rules and Side Effects::
* Destructive Operations::
* Evaluation and Compilation Dictionary::
@end menu
@node Evaluation, Compilation, Evaluation and Compilation, Evaluation and Compilation
@section Evaluation
@c including concept-eval
@i{Execution} of @i{code} can be accomplished by a variety of means ranging
from direct interpretation of a @i{form} representing a @i{program}
to invocation of @i{compiled code} produced by a @i{compiler}.
@i{Evaluation}
@IGindex{evaluation}
is the process by which a @i{program} is @i{executed} in @r{Common Lisp}.
The mechanism of @i{evaluation} is manifested
both implicitly through the effect of the @i{Lisp read-eval-print loop},
and explicitly through the presence of the @i{functions}
@b{eval},
@b{compile},
@b{compile-file},
and @b{load}.
Any of these facilities might share the same execution strategy,
or each might use a different one.
The behavior of a @i{conforming program} processed by @b{eval}
and by @b{compile-file} might differ; see @ref{Semantic Constraints}.
@i{Evaluation} can be understood in terms of a model in which an
interpreter recursively traverses a @i{form} performing each
step of the computation as it goes.
This model, which describes the semantics of @r{Common Lisp} @i{programs},
is described in @ref{The Evaluation Model}.
@menu
* Introduction to Environments::
* The Evaluation Model::
* Lambda Expressions::
* Closures and Lexical Binding::
* Shadowing::
* Extent::
* Return Values::
@end menu
@node Introduction to Environments, The Evaluation Model, Evaluation, Evaluation
@subsection Introduction to Environments
A @i{binding}
@IGindex{binding}
is an association between a @i{name} and
that which the name denotes. @i{Bindings} are @i{established}
in a @i{lexical environment} or a @i{dynamic environment}
by particular @i{special operators}.
An @i{environment}
@IGindex{environment}
is a set of @i{bindings} and other information
used during evaluation (@i{e.g.}, to associate meanings with names).
@i{Bindings} in an @i{environment} are partitioned into @i{namespaces}
@IGindex{namespace}
.
A single @i{name} can simultaneously have more than one
associated @i{binding} per @i{environment},
but can have only one associated @i{binding} per @i{namespace}.
@menu
* The Global Environment::
* Dynamic Environments::
* Lexical Environments::
* The Null Lexical Environment::
* Environment Objects::
@end menu
@node The Global Environment, Dynamic Environments, Introduction to Environments, Introduction to Environments
@subsubsection The Global Environment
The @i{global environment}
@IGindex{global environment}
is that part of an @i{environment}
that contains @i{bindings} with both @i{indefinite scope}
and @i{indefinite extent}.
The @i{global environment} contains, among other things, the following:
@table @asis
@item @t{*}
@i{bindings} of @i{dynamic variables} and @i{constant variables}.
@item @t{*}
@i{bindings} of @i{functions}, @i{macros}, and @i{special operators}.
@item @t{*}
@i{bindings} of @i{compiler macros}.
@item @t{*}
@i{bindings} of @i{type} and @i{class} @i{names}
@item @t{*}
information about @i{proclamations}.
@end table
@node Dynamic Environments, Lexical Environments, The Global Environment, Introduction to Environments
@subsubsection Dynamic Environments
A @i{dynamic environment}
@IGindex{dynamic environment}
for @i{evaluation} is that part of an
@i{environment} that contains @i{bindings} whose duration
is bounded by points of @i{establishment} and @i{disestablishment}
within the execution of the @i{form} that
established the @i{binding}.
A @i{dynamic environment} contains, among other things, the following:
@table @asis
@item @t{*}
@i{bindings} for @i{dynamic variables}.
@item @t{*}
information about @i{active} @i{catch tags}.
@item @t{*}
information about @i{exit points} established by @b{unwind-protect}.
@item @t{*}
information about @i{active} @i{handlers} and @i{restarts}.
@end table
The @i{dynamic environment} that is active at any given point
in the @i{execution} of a @i{program} is referred to by
definite reference as ``the current @i{dynamic environment},''
or sometimes as just ``the @i{dynamic environment}.''
Within a given @i{namespace},
a @i{name} is said to be @i{bound}
in a @i{dynamic environment} if there is a @i{binding}
associated with its @i{name} in the @i{dynamic environment}
or, if not, there is a @i{binding}
associated with its name in the @i{global environment}.
@node Lexical Environments, The Null Lexical Environment, Dynamic Environments, Introduction to Environments
@subsubsection Lexical Environments
A @i{lexical environment}
@IGindex{lexical environment}
for @i{evaluation} at some position in a @i{program}
is that part of the @i{environment} that contains information having
@i{lexical scope} within the @i{forms} containing that position.
A @i{lexical environment} contains, among other things, the following:
@table @asis
@item @t{*}
@i{bindings} of @i{lexical variables} and @i{symbol macros}.
@item @t{*}
@i{bindings} of @i{functions} and @i{macros}.
(Implicit in this is information about those @i{compiler macros}
that are locally disabled.)
@item @t{*}
@i{bindings} of @i{block tags}.
@item @t{*}
@i{bindings} of @i{go tags}.
@item @t{*}
information about @i{declarations}.
@end table
The @i{lexical environment} that is active at any given position
in a @i{program} being semantically processed is referred to by
definite reference as ``the current @i{lexical environment},''
or sometimes as just ``the @i{lexical environment}.''
Within a given @i{namespace},
a @i{name} is said to be @i{bound} in a @i{lexical environment}
if there is a @i{binding}
associated with its @i{name}
in the @i{lexical environment} or, if not, there is a @i{binding}
associated with its name in the @i{global environment}.
@node The Null Lexical Environment, Environment Objects, Lexical Environments, Introduction to Environments
@subsubsection The Null Lexical Environment
The @i{null lexical environment}
@IGindex{null lexical environment}
is equivalent to the @i{global environment}.
Although in general the representation of an @i{environment} @i{object}
is @i{implementation-dependent}, @b{nil} can be used in any situation where an
@i{environment} @i{object} is called for in order to denote
the @i{null lexical environment}.
@node Environment Objects, , The Null Lexical Environment, Introduction to Environments
@subsubsection Environment Objects
Some @i{operators} make use of an @i{object},
called an @i{environment object}
@IGindex{environment object}
,
that represents the set of @i{lexical bindings} needed to perform
semantic analysis on a @i{form} in a given @i{lexical environment}.
The set of @i{bindings} in an @i{environment object}
may be a subset of the @i{bindings} that would be needed to actually
perform an @i{evaluation}; for example, @i{values} associated with
@i{variable} @i{names} and @i{function names} in the corresponding
@i{lexical environment} might not be available in an @i{environment object}.
The @i{type} and nature of an @i{environment object} is @i{implementation-dependent}.
The @i{values} of @i{environment parameters} to @i{macro functions}
are examples of @i{environment objects}.
The @i{object} @b{nil} when used as an @i{environment object}
denotes the @i{null lexical environment};
see @ref{The Null Lexical Environment}.
@node The Evaluation Model, Lambda Expressions, Introduction to Environments, Evaluation
@subsection The Evaluation Model
A @r{Common Lisp} system evaluates @i{forms} with respect to lexical,
dynamic, and global @i{environments}. The following sections
describe the components of the @r{Common Lisp} evaluation model.
@menu
* Form Evaluation::
* Symbols as Forms::
* Lexical Variables::
* Dynamic Variables::
* Constant Variables::
* Symbols Naming Both Lexical and Dynamic Variables::
* Conses as Forms::
* Special Forms::
* Macro Forms::
* Function Forms::
* Lambda Forms::
* Self-Evaluating Objects::
* Examples of Self-Evaluating Objects::
@end menu
@node Form Evaluation, Symbols as Forms, The Evaluation Model, The Evaluation Model
@subsubsection Form Evaluation
@i{Forms} fall into three categories:
@i{symbols}, @i{conses}, and @i{self-evaluating objects}.
The following sections explain these categories.
@node Symbols as Forms, Lexical Variables, Form Evaluation, The Evaluation Model
@subsubsection Symbols as Forms
If a @i{form} is a @i{symbol},
then it is either a @i{symbol macro} or a @i{variable}.
The @i{symbol} names a @i{symbol macro}
if there is a @i{binding} of the @i{symbol} as a @i{symbol macro}
in the current @i{lexical environment}
(see @b{define-symbol-macro} and @b{symbol-macrolet}).
If the @i{symbol} is a @i{symbol macro},
its expansion function is obtained.
The expansion function is a function of two arguments, and is invoked
by calling the @i{macroexpand hook} with
the expansion function as its first argument,
the @i{symbol} as its second argument,
and an @i{environment object} (corresponding to the current @i{lexical environment})
as its third argument.
The @i{macroexpand hook}, in turn, calls the expansion function with the
@i{form} as its first argument and the @i{environment} as its second argument.
The @i{value} of the expansion function, which is passed through
by the @i{macroexpand hook}, is a @i{form}.
This resulting @i{form} is processed in place of the original @i{symbol}.
If a @i{form} is a @i{symbol} that is not a @i{symbol macro},
then it is the @i{name} of a @i{variable}, and the @i{value} of that
@i{variable} is returned. There are three kinds of variables:
@i{lexical variables},
@i{dynamic variables},
and
@i{constant variables}.
A @i{variable} can store one @i{object}.
The main operations on a @i{variable} are
to @i{read}_1 and
to @i{write}_1
its @i{value}.
An error of @i{type} @b{unbound-variable} should be signaled if
an @i{unbound variable} is referenced.
@i{Non-constant variables} can be @i{assigned} by using @b{setq}
or @i{bound}_3 by using @b{let}.
Figure 3--1 lists some @i{defined names} that
are applicable to assigning, binding, and defining @i{variables}.
@group
@noindent
@w{ boundp let progv }
@w{ defconstant let* psetq }
@w{ defparameter makunbound set }
@w{ defvar multiple-value-bind setq }
@w{ lambda multiple-value-setq symbol-value }
@noindent
@w{ Figure 3--1: Some Defined Names Applicable to Variables}
@end group
The following is a description of each kind of variable.
@node Lexical Variables, Dynamic Variables, Symbols as Forms, The Evaluation Model
@subsubsection Lexical Variables
A @i{lexical variable} is a @i{variable} that can be referenced only within
the @i{lexical scope} of the @i{form} that establishes that @i{variable};
@i{lexical variables} have @i{lexical scope}.
Each time a @i{form} creates a @i{lexical binding} of a @i{variable},
a @i{fresh} @i{binding} is @i{established}.
Within the @i{scope} of a @i{binding} for a @i{lexical variable} @i{name},
uses of that @i{name} as a @i{variable} are considered to be references
to that @i{binding} except where the @i{variable} is @i{shadowed}_2
by a @i{form} that @i{establishes} a @i{fresh} @i{binding} for that
@i{variable} @i{name},
or by a @i{form} that locally @i{declares} the @i{name} @b{special}.
A @i{lexical variable} always has a @i{value}.
There is no @i{operator} that introduces a @i{binding} for a
@i{lexical variable} without giving it an initial @i{value}, nor
is there any @i{operator} that can make a @i{lexical variable} be @i{unbound}.
@i{Bindings} of @i{lexical variables} are found in the @i{lexical environment}.
@node Dynamic Variables, Constant Variables, Lexical Variables, The Evaluation Model
@subsubsection Dynamic Variables
A @i{variable} is a @i{dynamic variable} if one of the following
conditions hold:
@table @asis
@item @t{*}
It is locally declared or globally proclaimed @b{special}.
@item @t{*}
It occurs textually within a @i{form} that
creates a @i{dynamic binding} for a @i{variable} of the @i{same} @i{name},
and the @i{binding} is not @i{shadowed}_2 by a @i{form}
that creates a @i{lexical binding} of the same @i{variable} @i{name}.
@end table
A @i{dynamic variable} can be referenced at any time in any @i{program};
there is no textual limitation on references to @i{dynamic variables}.
At any given time, all @i{dynamic variables} with a given name refer to
exactly one @i{binding}, either in the @i{dynamic environment}
or in the @i{global environment}.
The @i{value} part of the @i{binding} for a @i{dynamic variable} might
be empty; in this case, the @i{dynamic variable} is said to have no @i{value},
or to be @i{unbound}. A @i{dynamic variable} can be made @i{unbound}
by using @b{makunbound}.
The effect of @i{binding} a @i{dynamic variable} is to create
a new @i{binding} to which all references to that @i{dynamic variable}
in any @i{program} refer for the duration of the @i{evaluation} of the @i{form}
that creates the @i{dynamic binding}.
A @i{dynamic variable} can be referenced outside the @i{dynamic extent} of
a @i{form} that @i{binds} it. Such a @i{variable} is sometimes called
a ``global variable'' but is still in all respects just a @i{dynamic variable}
whose @i{binding} happens to exist in the @i{global environment} rather than in some
@i{dynamic environment}.
A @i{dynamic variable} is @i{unbound}
unless and until explicitly assigned a value, except for
those variables whose initial value is
defined in this specification or by an @i{implementation}.
@node Constant Variables, Symbols Naming Both Lexical and Dynamic Variables, Dynamic Variables, The Evaluation Model
@subsubsection Constant Variables
Certain variables, called @i{constant variables}, are reserved as ``named constants.''
The consequences are undefined if an attempt is made to
assign a value to,
or create
a @i{binding} for a @i{constant variable},
except that a `compatible' redefinition of a @i{constant variable}
using @b{defconstant} is permitted; see the @i{macro} @b{defconstant}.
@i{Keywords},
@i{symbols} defined by @r{Common Lisp} or the @i{implementation}
as constant (such as @b{nil}, @b{t}, and @b{pi}),
and @i{symbols} declared as constant using @b{defconstant}
are @i{constant variables}.
@node Symbols Naming Both Lexical and Dynamic Variables, Conses as Forms, Constant Variables, The Evaluation Model
@subsubsection Symbols Naming Both Lexical and Dynamic Variables
The same @i{symbol} can name both
a @i{lexical variable}
and a @i{dynamic variable},
but never in the same @i{lexical environment}.
In the following example, the @i{symbol} @t{x} is used,
at different times,
as the @i{name} of a @i{lexical variable}
and as the @i{name} of a @i{dynamic variable}.
@example
(let ((x 1)) ;Binds a special variable X
(declare (special x))
(let ((x 2)) ;Binds a lexical variable X
(+ x ;Reads a lexical variable X
(locally (declare (special x))
x)))) ;Reads a special variable X
@result{} 3
@end example
@node Conses as Forms, Special Forms, Symbols Naming Both Lexical and Dynamic Variables, The Evaluation Model
@subsubsection Conses as Forms
A @i{cons} that is used as a @i{form} is called a @i{compound form}.
If the @i{car} of that @i{compound form} is a @i{symbol},
that @i{symbol} is the @i{name} of an @i{operator},
and the @i{form} is either a @i{special form}, a @i{macro form},
or a @i{function form}, depending on the @i{function} @i{binding}
of the @i{operator} in the current @i{lexical environment}.
If the @i{operator} is neither a @i{special operator}
nor a @i{macro name}, it is assumed to be a @i{function name}
(even if there is no definition for such a @i{function}).
If the @i{car} of the @i{compound form} is not a @i{symbol},
then that @i{car} must be a @i{lambda expression},
in which case the @i{compound form} is a @i{lambda form}.
How a @i{compound form} is processed depends on whether it is
classified as a @i{special form}, a @i{macro form},
a @i{function form}, or a @i{lambda form}.
@node Special Forms, Macro Forms, Conses as Forms, The Evaluation Model
@subsubsection Special Forms
A @i{special form} is a @i{form} with special syntax,
special evaluation rules, or both, possibly manipulating the
evaluation environment, control flow, or both.
A @i{special operator} has access to
the current @i{lexical environment}
and the current @i{dynamic environment}.
Each @i{special operator} defines the manner in which its @i{subexpressions}
are treated---which are @i{forms}, which are special syntax, @i{etc.}
Some @i{special operators} create new
lexical or dynamic @i{environments} for use during the
@i{evaluation} of @i{subforms}
of the @i{special form}. For example, @b{block} creates a
new @i{lexical environment} that is the same as the one in force
at the point of evaluation of the @b{block} @i{form}
with the addition of a @i{binding} of the @b{block} name
to an @i{exit point} from the @b{block}.
The set of @i{special operator} @i{names} is fixed in @r{Common Lisp};
no way is provided for the user to define a @i{special operator}.
Figure 3--2 lists all of the @r{Common Lisp} @i{symbols}
that have definitions as @i{special operators}.
@group
@noindent
@w{ block let* return-from }
@w{ catch load-time-value setq }
@w{ eval-when locally symbol-macrolet }
@w{ flet macrolet tagbody }
@w{ function multiple-value-call the }
@w{ go multiple-value-prog1 throw }
@w{ if progn unwind-protect }
@w{ labels progv }
@w{ let quote }
@noindent
@w{ Figure 3--2: Common Lisp Special Operators }
@end group
@node Macro Forms, Function Forms, Special Forms, The Evaluation Model
@subsubsection Macro Forms
If the @i{operator} names a @i{macro},
its associated @i{macro function} is applied
to the entire @i{form} and the result of that application is
used in place of the original @i{form}.
Specifically, a @i{symbol} names a @i{macro} in a given @i{lexical environment} if
@b{macro-function} is @i{true} of the
@i{symbol} and that @i{environment}.
The @i{function} returned by @b{macro-function}
is a @i{function} of two arguments, called the
expansion function.
The expansion function is invoked by calling the @i{macroexpand hook} with
the expansion function as its first argument,
the entire @i{macro form} as its second argument,
and an @i{environment object} (corresponding to the current @i{lexical environment})
as its third argument.
The @i{macroexpand hook}, in turn, calls the expansion function with the
@i{form} as its first argument and the @i{environment} as its second argument.
The @i{value} of the expansion function, which is passed through
by the @i{macroexpand hook}, is a @i{form}.
The returned @i{form} is @i{evaluated} in place of the original @i{form}.
The consequences are undefined if a @i{macro function} destructively modifies
any part of its @i{form} argument.
A @i{macro name} is not a @i{function designator},
and cannot be used as the @i{function} argument to @i{functions}
such as @b{apply}, @b{funcall}, or @b{map}.
An @i{implementation} is free to implement a @r{Common Lisp} @i{special operator}
as a @i{macro}. An @i{implementation} is free to implement any
@i{macro} @i{operator} as a @i{special operator}, but only
if an equivalent definition of the @i{macro} is also provided.
Figure 3--3 lists some @i{defined names} that are applicable
to @i{macros}.
@group
@noindent
@w{ *macroexpand-hook* macro-function macroexpand-1 }
@w{ defmacro macroexpand macrolet }
@noindent
@w{ Figure 3--3: Defined names applicable to macros }
@end group
@node Function Forms, Lambda Forms, Macro Forms, The Evaluation Model
@subsubsection Function Forms
If the @i{operator} is a @i{symbol} naming a @i{function},
the @i{form} represents a @i{function form},
and the @i{cdr} of the list contains the @i{forms}
which when evaluated will supply the arguments passed to the @i{function}.
When a @i{function name} is not defined,
an error of @i{type} @b{undefined-function} should be signaled at run time;
see @ref{Semantic Constraints}.
A @i{function form} is evaluated as follows:
The @i{subforms} in the @i{cdr} of the original @i{form}
are evaluated in left-to-right order in the current lexical and
dynamic @i{environments}. The @i{primary value} of each
such @i{evaluation} becomes an @i{argument} to the named @i{function};
any additional @i{values} returned by the @i{subforms} are discarded.
The @i{functional value} of the @i{operator}
is retrieved from the @i{lexical environment},
and that @i{function} is invoked with the indicated arguments.
Although the order of @i{evaluation} of
the @i{argument} @i{subforms} themselves is
strictly left-to-right, it is not specified whether
the definition of the @i{operator} in a @i{function form} is looked up
before the @i{evaluation} of the @i{argument} @i{subforms},
after the @i{evaluation} of the @i{argument} @i{subforms},
or between the @i{evaluation} of any two @i{argument} @i{subforms}
if there is more than one such @i{argument} @i{subform}.
For example, the following might return 23 or~24.
@example
(defun foo (x) (+ x 3))
(defun bar () (setf (symbol-function 'foo) #'(lambda (x) (+ x 4))))
(foo (progn (bar) 20))
@end example
A @i{binding} for a @i{function name} can be @i{established} in
one of several ways. A @i{binding} for a @i{function name} in
the @i{global environment} can be @i{established} by
@b{defun},
@b{setf} of @b{fdefinition},
@b{setf} of @b{symbol-function},
@b{ensure-generic-function},
@b{defmethod} (implicitly, due to @b{ensure-generic-function}),
or
@b{defgeneric}.
A @i{binding} for a @i{function name} in the @i{lexical environment}
can be @i{established} by
@b{flet}
or @b{labels}.
Figure 3--4 lists some @i{defined names} that are applicable to @i{functions}.
@group
@noindent
@w{ apply fdefinition mapcan }
@w{ call-arguments-limit flet mapcar }
@w{ complement fmakunbound mapcon }
@w{ constantly funcall mapl }
@w{ defgeneric function maplist }
@w{ defmethod functionp multiple-value-call }
@w{ defun labels reduce }
@w{ fboundp map symbol-function }
@noindent
@w{ Figure 3--4: Some function-related defined names }
@end group
@node Lambda Forms, Self-Evaluating Objects, Function Forms, The Evaluation Model
@subsubsection Lambda Forms
A @i{lambda form} is similar to a @i{function form}, except that
the @i{function name} is replaced by a @i{lambda expression}.
A @i{lambda form} is equivalent to using @i{funcall} of a
@i{lexical closure} of the @i{lambda expression} on the given @i{arguments}.
(In practice, some compilers are more likely to produce inline code
for a @i{lambda form} than for an arbitrary named function
that has been declared @b{inline}; however, such a difference
is not semantic.)
For further information, see @ref{Lambda Expressions}.
@node Self-Evaluating Objects, Examples of Self-Evaluating Objects, Lambda Forms, The Evaluation Model
@subsubsection Self-Evaluating Objects
A @i{form} that is neither a @i{symbol} nor a @i{cons} is
defined to be a @i{self-evaluating object}. @i{Evaluating}
such an @i{object} @i{yields} the @i{same} @i{object}
as a result.
Certain specific @i{symbols} and @i{conses} might also happen
to be ``self-evaluating'' but only as a special case of a more
general set of rules for the @i{evaluation} of @i{symbols} and
@i{conses}; such @i{objects} are not considered to be
@i{self-evaluating objects}.
The consequences are undefined if @i{literal objects} (including
@i{self-evaluating objects}) are destructively modified.
@node Examples of Self-Evaluating Objects, , Self-Evaluating Objects, The Evaluation Model
@subsubsection Examples of Self-Evaluating Objects
@i{Numbers}, @i{pathnames}, and @i{arrays} are examples of
@i{self-evaluating objects}.
@example
3 @result{} 3
#c(2/3 5/8) @result{} #C(2/3 5/8)
#p"S:[BILL]OTHELLO.TXT" @result{} #P"S:[BILL]OTHELLO.TXT"
#(a b c) @result{} #(A B C)
"fred smith" @result{} "fred smith"
@end example
@node Lambda Expressions, Closures and Lexical Binding, The Evaluation Model, Evaluation
@subsection Lambda Expressions
In a @i{lambda expression},
the body is evaluated in a lexical @i{environment} that is formed by
adding the @i{binding} of
each @i{parameter} in the @i{lambda list}
with the corresponding @i{value} from the @i{arguments}
to the current lexical @i{environment}.
For further discussion of how @i{bindings} are @i{established}
based on the @i{lambda list}, see @ref{Lambda Lists}.
The body of a @i{lambda expression} is an @i{implicit progn};
the @i{values} it returns are returned by the @i{lambda expression}.
@node Closures and Lexical Binding, Shadowing, Lambda Expressions, Evaluation
@subsection Closures and Lexical Binding
A @i{lexical closure} is a @i{function} that can refer to and alter
the values of @i{lexical bindings} @i{established} by @i{binding} @i{forms}
that textually include the function definition.
Consider this code, where @t{x} is not declared @b{special}:
@example
(defun two-funs (x)
(list (function (lambda () x))
(function (lambda (y) (setq x y)))))
(setq funs (two-funs 6))
(funcall (car funs)) @result{} 6
(funcall (cadr funs) 43) @result{} 43
(funcall (car funs)) @result{} 43
@end example
The @b{function} @i{special form} coerces a
@i{lambda expression} into a @i{closure} in which the
@i{lexical environment} in effect when the @i{special form} is
evaluated is captured along with the @i{lambda expression}.
The function @t{two-funs} returns a @i{list} of two
@i{functions}, each of which refers to the @i{binding} of the
variable @t{x} created on entry to the function @t{two-funs} when it
was called.
This variable has the value @t{6}
initially, but @b{setq} can alter this @i{binding}.
The @i{lexical closure} created for the first
@i{lambda expression} does not ``snapshot'' the @i{value} @t{6} for @t{x}
when the @i{closure} is created; rather it captures the @i{binding} of @t{x}.
The second @i{function} can be used to alter the @i{value} in the same (captured)
@i{binding} (to @t{43}, in the example), and
this altered variable binding then affects the value returned by the first @i{function}.
In situations where a @i{closure} of a
@i{lambda expression} over the same set of @i{bindings} may be
produced more than once, the various resulting @i{closures} may
or may not be @i{identical}, at the discretion of the @i{implementation}.
That is, two @i{functions} that are behaviorally
indistinguishable might or might not be @i{identical}.
Two @i{functions} that are behaviorally distinguishable are @i{distinct}.
For example:
@example
(let ((x 5) (funs '()))
(dotimes (j 10)
(push #'(lambda (z)
(if (null z) (setq x 0) (+ x z)))
funs))
funs)
@end example
The result of the above @i{form} is a @i{list} of ten @i{closures}.
Each requires only the @i{binding} of @t{x}.
It is the same @i{binding} in each case,
but the ten @i{closure} @i{objects} might or might not be @i{identical}.
On the other hand, the result of the @i{form}
@example
(let ((funs '()))
(dotimes (j 10)
(let ((x 5))
(push (function (lambda (z)
(if (null z) (setq x 0) (+ x z))))
funs)))
funs)
@end example
is also a @i{list} of ten @i{closures}.
However, in this case no two of the @i{closure} @i{objects} can
be @i{identical} because each @i{closure} is closed over a distinct
@i{binding} of @t{x}, and these @i{bindings} can be behaviorally
distinguished because of the use of @b{setq}.
The result of the @i{form}
@example
(let ((funs '()))
(dotimes (j 10)
(let ((x 5))
(push (function (lambda (z) (+ x z)))
funs)))
funs)
@end example
is a @i{list} of ten @i{closure} @i{objects} that
might or might not be @i{identical}.
A different @i{binding} of @t{x} is involved for
each @i{closure}, but the @i{bindings} cannot be distinguished
because their values are the @i{same} and immutable (there being no occurrence
of @b{setq} on @t{x}). A compiler could internally
transform the @i{form} to
@example
(let ((funs '()))
(dotimes (j 10)
(push (function (lambda (z) (+ 5 z)))
funs))
funs)
@end example
where the @i{closures} may be @i{identical}.
It is possible that a @i{closure} does not
close over any variable bindings.
In the code fragment
@example
(mapcar (function (lambda (x) (+ x 2))) y)
@end example
the function @t{(lambda (x) (+ x 2))} contains no references to any outside
object. In this case, the same @i{closure} might be returned
for all evaluations of the @b{function} @i{form}.
@node Shadowing, Extent, Closures and Lexical Binding, Evaluation
@subsection Shadowing
If two @i{forms} that @i{establish} @i{lexical bindings} with
the same @i{name} N are textually nested, then references to N
within the inner @i{form} refer to the @i{binding} established by
the inner @i{form}; the inner @i{binding} for N
@i{shadows}
@IGindex{shadow}
the outer @i{binding} for N. Outside the inner
@i{form} but inside the outer one, references to N refer to the
@i{binding} established by the outer @i{form}. For example:
@example
(defun test (x z)
(let ((z (* x 2)))
(print z))
z)
@end example
The @i{binding} of the variable @t{z} by
@b{let} shadows
the @i{parameter} binding for the function @t{test}. The reference to the
variable @t{z} in the @b{print} @i{form} refers to the @b{let} binding.
The reference to @t{z} at the end of the function @t{test}
refers to the @i{parameter} named @t{z}.
Constructs that are lexically scoped act as if new names were
generated for each @i{object} on each execution. Therefore,
dynamic shadowing cannot occur. For example:
@example
(defun contorted-example (f g x)
(if (= x 0)
(funcall f)
(block here
(+ 5 (contorted-example g
#'(lambda () (return-from here 4))
(- x 1))))))
@end example
Consider the call @t{(contorted-example nil nil 2)}. This produces
@t{4}. During the course of execution, there are three
calls to @t{contorted-example}, interleaved with two
blocks:
@example
(contorted-example nil nil 2)
(block here{{}_1} ...)
(contorted-example nil #'(lambda () (return-from here{{}_1} 4)) 1)
(block here{{}_2} ...)
(contorted-example #'(lambda () (return-from here{{}_1} 4))
#'(lambda () (return-from here{{}_2} 4))
0)
(funcall f)
where f @result{} #'(lambda () (return-from here{{}_1} 4))
(return-from here{{}_1} 4)
@end example
At the time the @t{funcall} is executed
there are two @b{block} @i{exit points} outstanding, each apparently
named @t{here}.
The @b{return-from} @i{form} executed as a result of the @t{funcall}
operation
refers to the outer outstanding @i{exit point}
(here{{}_1}), not the
inner one (here{{}_2}).
It
refers to that @i{exit point} textually visible at the point of
execution of @b{function}
(here abbreviated by the @t{#'} syntax) that resulted
in creation of the @i{function} @i{object} actually invoked by
@b{funcall}.
If, in this example, one were to change the @t{(funcall f)} to
@t{(funcall g)}, then the value of the call @t{(contorted-example nil nil 2)}
would be @t{9}. The value would change because
@b{funcall} would cause the
execution of @t{(return-from here{{}_2} 4)}, thereby causing
a return from the inner @i{exit point} (here{{}_2}).
When that occurs, the value @t{4} is returned from the
middle invocation of @t{contorted-example}, @t{5} is added to that
to get @t{9}, and that value is returned from the outer block
and the outermost call to @t{contorted-example}. The point
is that the choice of @i{exit point}
returned from has nothing to do with its
being innermost or outermost; rather,
it depends on the lexical environment
that is packaged up with a @i{lambda expression} when
@b{function} is executed.
@node Extent, Return Values, Shadowing, Evaluation
@subsection Extent
@t{Contorted-example} works only because the
@i{function} named by @t{f} is invoked during the @i{extent} of the
@i{exit point}.
Once the flow of execution has left the block,
the @i{exit point} is @i{disestablished}. For example:
@example
(defun invalid-example ()
(let ((y (block here #'(lambda (z) (return-from here z)))))
(if (numberp y) y (funcall y 5))))
@end example
One might expect the call @t{(invalid-example)} to produce @t{5}
by the following incorrect reasoning:
@b{let} binds @t{y} to the
value of @b{block}; this value is a @i{function} resulting
from the @i{lambda expression}. Because @t{y} is not a number, it is
invoked on the value @t{5}. The @b{return-from} should then
return this value from the
@i{exit point} named @t{here}, thereby
exiting from the block again and giving @t{y} the value @t{5}
which, being a number, is then returned as the value of the call
to @t{invalid-example}.
The argument fails only because @i{exit points} have
@i{dynamic extent}. The argument is correct up to the execution of
@b{return-from}. The execution of @b{return-from}
should signal an error of @i{type} @b{control-error}, however, not
because it cannot refer to the @i{exit point}, but because it
does correctly refer to an @i{exit point} and that
@i{exit point} has been @i{disestablished}.
A reference by name to a dynamic @i{exit point} binding such as
a @i{catch tag} refers to the most recently
@i{established} @i{binding} of that name that has not been
@i{disestablished}. For example:
@example
(defun fun1 (x)
(catch 'trap (+ 3 (fun2 x))))
(defun fun2 (y)
(catch 'trap (* 5 (fun3 y))))
(defun fun3 (z)
(throw 'trap z))
@end example
Consider the call @t{(fun1 7)}. The result is @t{10}. At the time
the @b{throw} is executed, there are two outstanding catchers with the
name @t{trap}: one established within procedure @t{fun1}, and the other
within procedure @t{fun2}. The latter is the more recent, and so the
value @t{7} is returned from @b{catch} in @t{fun2}.
Viewed from within @t{fun3}, the @b{catch}
in @t{fun2} shadows the one in @t{fun1}.
Had @t{fun2} been defined as
@example
(defun fun2 (y)
(catch 'snare (* 5 (fun3 y))))
@end example
then the two @i{exit points}
would have different @i{names}, and therefore the one
in @t{fun1} would not be shadowed. The result would then have been @t{7}.
@node Return Values, , Extent, Evaluation
@subsection Return Values
Ordinarily the result of calling a @i{function} is a single @i{object}.
Sometimes, however, it is convenient for a function to compute several
@i{objects} and return them.
In order to receive other than exactly one value from a @i{form},
one of several @i{special forms} or @i{macros} must be used to request those
values. If a @i{form} produces @i{multiple values} which were not
requested in this way, then the first value is given to the caller and
all others are discarded; if the @i{form} produces zero values,
then the caller receives @b{nil} as a value.
Figure 3--5 lists
some @i{operators} for receiving @i{multiple values}_2.
These @i{operators} can be used to specify
one or more @i{forms} to @i{evaluate}
and where to put the @i{values} returned by those @i{forms}.
@group
@noindent
@w{ multiple-value-bind multiple-value-prog1 return-from }
@w{ multiple-value-call multiple-value-setq throw }
@w{ multiple-value-list return }
@noindent
@w{ Figure 3--5: Some operators applicable to receiving multiple values}
@end group
The @i{function} @b{values} can produce @i{multiple values}_2.
@t{(values)} returns zero values;
@t{(values @i{form})} returns the @i{primary value} returned by @i{form};
@t{(values @i{form1} @i{form2})} returns two values,
the @i{primary value} of @i{form1}
and the @i{primary value} of @i{form2};
and so on.
See @b{multiple-values-limit} and @b{values-list}.
@c end of including concept-eval
@node Compilation, Declarations, Evaluation, Evaluation and Compilation
@section Compilation
@c including concept-compile
@menu
* Compiler Terminology::
* Compilation Semantics::
* File Compilation::
* Literal Objects in Compiled Files::
* Exceptional Situations in the Compiler::
@end menu
@node Compiler Terminology, Compilation Semantics, Compilation, Compilation
@subsection Compiler Terminology
The following terminology is used in this section.
The @i{compiler}
@IGindex{compiler}
is a utility that translates code into an
@i{implementation-dependent} form that might be represented or
executed efficiently.
The term @i{compiler}
@IGindex{compiler}
refers to both of the @i{functions}
@b{compile} and @b{compile-file}.
The term @i{compiled code}
@IGindex{compiled code}
refers to
@i{objects} representing compiled programs, such as @i{objects} constructed
by @b{compile} or by @b{load} when @i{loading} a @i{compiled file}.
The term @i{implicit compilation}
@IGindex{implicit compilation}
refers to @i{compilation}
performed during @i{evaluation}.
The term @i{literal object}
@IGindex{literal object}
refers to
a quoted @i{object}
or a @i{self-evaluating object}
or an @i{object} that is a substructure of such an @i{object}.
A @i{constant variable} is not itself a @i{literal object}.
The term @i{coalesce}
@IGindex{coalesce}
is defined as follows.
Suppose @t{A} and @t{B} are two @i{literal constants} in the @i{source code},
and that @t{A'} and @t{B'} are the corresponding @i{objects} in the @i{compiled code}.
If @t{A'} and @t{B'} are @b{eql} but
@t{A} and @t{B} are not @b{eql}, then it is said
that @t{A} and @t{B} have been coalesced by the compiler.
The term @i{minimal compilation}
@IGindex{minimal compilation}
refers to actions the compiler
must take at @i{compile time}. These actions are specified in
@ref{Compilation Semantics}.
The verb @i{process}
@IGindex{process}
refers to performing @i{minimal compilation},
determining the time of evaluation for a @i{form},
and possibly @i{evaluating} that @i{form} (if required).
The term @i{further compilation}
@IGindex{further compilation}
refers to
@i{implementation-dependent} compilation beyond @i{minimal compilation}.
That is, @i{processing} does not imply complete compilation.
Block compilation and generation of machine-specific instructions are
examples of further compilation.
Further compilation is permitted to take place at @i{run time}.
Four different @i{environments} relevant to compilation are
distinguished:
the @i{startup environment},
the @i{compilation environment},
the @i{evaluation environment}, and
the @i{run-time environment}.
The @i{startup environment}
@IGindex{startup environment}
is
the @i{environment} of the @i{Lisp image}
from which the @i{compiler} was invoked.
The @i{compilation environment}
@IGindex{compilation environment}
is maintained by the compiler
and is used to hold definitions and declarations to be used internally
by the compiler. Only those parts of a definition needed for correct
compilation are saved. The @i{compilation environment} is used
as the @i{environment} @i{argument} to macro expanders called by
the compiler. It is unspecified whether a definition available in the
@i{compilation environment} can be used in an @i{evaluation}
initiated in the @i{startup environment} or @i{evaluation environment}.
The @i{evaluation environment}
@IGindex{evaluation environment}
is a @i{run-time environment}
in which macro expanders and code specified by @b{eval-when}
to be evaluated are evaluated. All evaluations initiated by the
@i{compiler} take place in the @i{evaluation environment}.
The @i{run-time environment}
@IGindex{run-time environment}
is the
@i{environment} in which the program being compiled will be executed.
The @i{compilation environment} inherits from
the @i{evaluation environment},
and the @i{compilation environment} and @i{evaluation environment}
might be @i{identical}.
The @i{evaluation environment} inherits from
the @i{startup environment},
and the @i{startup environment} and @i{evaluation environment}
might be @i{identical}.
The term @i{compile time}
@IGindex{compile time}
refers to the duration of time that
the compiler is processing @i{source code}.
At @i{compile time},
only the @i{compilation environment}
and the @i{evaluation environment}
are available.
The term @i{compile-time definition}
@IGindex{compile-time definition}
refers to a definition in
the @i{compilation environment}.
For example, when compiling a file,
the definition of a function might be retained in the @i{compilation environment}
if it is declared @b{inline}.
This definition might not be available in the @i{evaluation environment}.
The term @i{run time}
@IGindex{run time}
refers to the duration of time that the
loader is loading compiled code or compiled code is being executed.
At run time, only the @i{run-time environment} is available.
The term @i{run-time definition}
@IGindex{run-time definition}
refers to a definition in the
@i{run-time environment}.
The term @i{run-time compiler}
@IGindex{run-time compiler}
refers to the @i{function} @b{compile}
or @i{implicit compilation}, for which the compilation and run-time
@i{environments} are maintained in the same @i{Lisp image}.
Note that when the @i{run-time compiler} is used,
the @i{run-time environment}
and @i{startup environment}
are the same.
@node Compilation Semantics, File Compilation, Compiler Terminology, Compilation
@subsection Compilation Semantics
Conceptually, compilation is a process that traverses code, performs
certain kinds of syntactic and semantic analyses using information
(such as proclamations and @i{macro} definitions) present in the
@i{compilation environment}, and produces equivalent, possibly
more efficient code.
@menu
* Compiler Macros::
* Purpose of Compiler Macros::
* Naming of Compiler Macros::
* When Compiler Macros Are Used::
* Notes about the Implementation of Compiler Macros::
* Minimal Compilation::
* Semantic Constraints::
@end menu
@node Compiler Macros, Purpose of Compiler Macros, Compilation Semantics, Compilation Semantics
@subsubsection Compiler Macros
A @i{compiler macro} can be defined for a @i{name}
that also names a @i{function} or @i{macro}.
That is, it is possible for a
@i{function name} to name both a @i{function} and a @i{compiler macro}.
A @i{function name} names a @i{compiler macro} if @b{compiler-macro-function}
is @i{true} of the @i{function name} in the @i{lexical environment} in which
it appears. Creating a @i{lexical binding} for the @i{function name}
not only creates a new local @i{function} or
@i{macro} definition, but also @i{shadows}_2 the @i{compiler macro}.
The @i{function} returned by @b{compiler-macro-function}
is a @i{function} of two arguments, called the
expansion function. To expand a @i{compiler macro},
the expansion function is invoked by calling the @i{macroexpand hook} with
the expansion function as its first argument,
the entire compiler macro @i{form} as its second argument,
and the current compilation @i{environment}
(or with the current lexical @i{environment},
if the @i{form} is being processed by something
other than @b{compile-file})
as its third argument.
The @i{macroexpand hook}, in turn, calls the expansion function with the
@i{form} as its first argument and the @i{environment} as its second argument.
The return value from the expansion function, which is passed through
by the @i{macroexpand hook}, might either be the @i{same} @i{form},
or else a form that can, at the discretion of the @i{code} doing the expansion,
be used in place of the original @i{form}.
@group
@noindent
@w{ *macroexpand-hook* compiler-macro-function define-compiler-macro }
@noindent
@w{ Figure 3--6: Defined names applicable to compiler macros }
@end group
@node Purpose of Compiler Macros, Naming of Compiler Macros, Compiler Macros, Compilation Semantics
@subsubsection Purpose of Compiler Macros
The purpose of the @i{compiler macro} facility is to permit
selective source code transformations as optimization advice
to the @i{compiler}. When a @i{compound form} is being
processed (as by the compiler), if the @i{operator} names a
@i{compiler macro} then the @i{compiler macro function} may be
invoked on the form, and the resulting expansion recursively processed
in preference to performing the usual processing on the original @i{form}
according to its normal interpretation as a @i{function form} or
@i{macro form}.
A @i{compiler macro function}, like a @i{macro function},
is a @i{function} of two @i{arguments}: the entire call @i{form}
and the @i{environment}. Unlike an ordinary @i{macro function}, a
@i{compiler macro function} can decline to provide an expansion merely by
returning a value that is the @i{same} as the original @i{form}.
The consequences are undefined if a @i{compiler macro function}
destructively modifies any part of its @i{form} argument.
The @i{form} passed to the compiler macro function can either be a @i{list}
whose @i{car} is the function name, or a @i{list} whose @i{car} is
@b{funcall} and whose @i{cadr} is a list @t{(function @i{name})};
note that this affects destructuring of the form argument by the
@i{compiler macro function}.
@b{define-compiler-macro} arranges for destructuring of arguments to be
performed correctly for both possible formats.
When @b{compile-file} chooses to expand a @i{top level form} that is
a @i{compiler macro} @i{form}, the expansion is also treated as a @i{top level form}
for the purposes of @b{eval-when} processing; see @ref{Processing of Top Level Forms}.
@node Naming of Compiler Macros, When Compiler Macros Are Used, Purpose of Compiler Macros, Compilation Semantics
@subsubsection Naming of Compiler Macros
@i{Compiler macros} may be defined for @i{function names} that name
@i{macros} as well as @i{functions}.
@i{Compiler macro} definitions are strictly global. There is no provision
for defining local @i{compiler macros} in the way that @b{macrolet}
defines local @i{macros}. Lexical bindings of a function name shadow any
compiler macro definition associated with the name as well as its
global @i{function} or @i{macro} definition.
Note that the presence of a compiler macro definition does not affect
the values returned by
functions that access @i{function} definitions (@i{e.g.}, @b{fboundp})
or @i{macro} definitions (@i{e.g.}, @b{macroexpand}).
Compiler macros are global, and the function
@b{compiler-macro-function} is sufficient to resolve their interaction
with other lexical and global definitions.
@node When Compiler Macros Are Used, Notes about the Implementation of Compiler Macros, Naming of Compiler Macros, Compilation Semantics
@subsubsection When Compiler Macros Are Used
The presence of a @i{compiler macro} definition for a @i{function} or @i{macro}
indicates that it is desirable for the @i{compiler} to use the expansion
of the @i{compiler macro} instead of the original @i{function form} or
@i{macro form}. However, no language processor
(compiler, evaluator, or other code walker) is ever required to actually
invoke @i{compiler macro functions}, or to
make use of the resulting expansion if it does invoke
a @i{compiler macro function}.
When the @i{compiler} encounters a @i{form} during processing that represents
a call to a @i{compiler macro} @i{name} (that is not declared @b{notinline}),
the @i{compiler} might expand the @i{compiler macro},
and might use the expansion in place of the original @i{form}.
When @b{eval} encounters a @i{form} during processing that represents
a call to a @i{compiler macro} @i{name} (that is not declared @b{notinline}),
@b{eval} might expand the @i{compiler macro},
and might use the expansion in place of the original @i{form}.
There are two situations in which a @i{compiler macro} definition must not be
applied by any language processor:
@table @asis
@item @t{*}
The global function name binding associated with the compiler
macro is shadowed by a lexical binding of the function name.
@item @t{*}
The function name has been declared or proclaimed @b{notinline} and
the call form appears within the scope of the declaration.
@end table
It is unspecified whether @i{compiler macros} are expanded or used in any other
situations.
@node Notes about the Implementation of Compiler Macros, Minimal Compilation, When Compiler Macros Are Used, Compilation Semantics
@subsubsection Notes about the Implementation of Compiler Macros
Although it is technically permissible, as described above,
for @b{eval} to treat @i{compiler macros} in the same situations
as @i{compiler} might, this is not necessarily a good idea in
@i{interpreted implementations}.
@i{Compiler macros} exist for the purpose of trading compile-time speed
for run-time speed. Programmers who write @i{compiler macros} tend to
assume that the @i{compiler macros} can take more time than normal @i{functions}
and @i{macros} in order to produce code which is especially optimal for use
at run time. Since @b{eval} in an @i{interpreted implementation}
might perform semantic analysis of the same form multiple times, it might be
inefficient in general for the @i{implementation} to choose to call
@i{compiler macros} on every such @i{evaluation}.
Nevertheless, the decision about what to do in these situations is left to
each @i{implementation}.
@node Minimal Compilation, Semantic Constraints, Notes about the Implementation of Compiler Macros, Compilation Semantics
@subsubsection Minimal Compilation
@i{Minimal compilation} is defined as follows:
@table @asis
@item @t{*}
All @i{compiler macro}
@IGindex{compiler macro}
calls appearing in the
@i{source code} being compiled are expanded, if at all, at compile time;
they will not be expanded at run time.
@item @t{*}
All @i{macro}
@IGindex{macro}
and
@i{symbol macro}
@IGindex{symbol macro}
calls
appearing in the source code being compiled are expanded at compile time
in such a way that they will not be expanded again at run time.
@b{macrolet}
@IRindex{macrolet}
and
@b{symbol-macrolet}
@IRindex{symbol-macrolet}
are effectively replaced by
@i{forms} corresponding to their bodies in which calls to
@i{macros} are replaced by their expansions.
@item @t{*}
The first @i{argument} in a @b{load-time-value}
@IRindex{load-time-value}
@i{form}
in @i{source code} processed by @b{compile}
@IRindex{compile}
is @i{evaluated} at @i{compile time};
in @i{source code} processed by @b{compile-file}
@IRindex{compile-file}
,
the compiler arranges for it to be @i{evaluated} at @i{load time}.
In either case, the result of the @i{evaluation}
is remembered and used later as the value of the
@b{load-time-value} @i{form} at @i{execution time}.
@end table
@node Semantic Constraints, , Minimal Compilation, Compilation Semantics
@subsubsection Semantic Constraints
All @i{conforming programs} must obey the following constraints,
which are designed to minimize the observable differences
between compiled and interpreted programs:
@table @asis
@item @t{*}
Definitions of any referenced @i{macros}
must be present in the @i{compilation environment}.
Any @i{form} that is a @i{list}
beginning with a @i{symbol} that does not name a
@i{special operator} or a @i{macro} defined in the
@i{compilation environment} is treated by the compiler as a
function call.
@item @t{*}
@b{Special} proclamations for @i{dynamic variables}
must be made in the @i{compilation environment}. Any @i{binding}
for which there is no @b{special} declaration or proclamation in
the @i{compilation environment} is treated by the compiler as
a @i{lexical binding}.
@item @t{*}
The definition of a function that is defined and
declared @b{inline} in the @i{compilation environment} must be
the same at run time.
@item @t{*}
Within a @i{function} named F, the compiler may
(but is not required to)
assume that an apparent recursive call to a @i{function} named F
refers to the same definition of F,
unless that function has been declared @b{notinline}.
The consequences of redefining such a recursively defined @i{function} F
while it is executing are undefined.
@item @t{*}
A call within a file to a named function that is
defined in the same file refers to that function, unless that function
has been declared @b{notinline}. The consequences are unspecified
if functions are redefined individually at run time or multiply
defined in the same file.
@item @t{*}
The argument syntax and number of return values for
all functions whose @b{ftype} is declared at compile time must
remain the same at run time.
@item @t{*}
@i{Constant variables} defined in
the @i{compilation environment} must have a @i{similar} value at
run time. A reference to
a @i{constant variable}
in @i{source code} is equivalent to a reference to
a @i{literal} @i{object} that is the @i{value} of the @i{constant variable}.
@item @t{*}
Type definitions made with @b{deftype} or
@b{defstruct} in the @i{compilation environment} must
retain the same definition at run time. Classes defined by @b{defclass}
in the @i{compilation environment} must be defined
at run time to have the same @i{superclasses} and same
@i{metaclass}.
This implies that @i{subtype}/@i{supertype} relationships of
@i{type specifiers} must not change between @i{compile time} and @i{run time}.
@item @t{*}
Type declarations present in the compilation
@i{environment} must accurately describe the corresponding values at run time;
otherwise, the consequences are undefined. It is permissible
for an unknown @i{type} to appear in a declaration at
compile time, though a warning might be signaled in such a case.
@item @t{*}
Except in the situations explicitly listed above, a
@i{function} defined in the @i{evaluation environment}
is permitted to have a different definition or a different @i{signature}
at run time, and the run-time definition prevails.
@end table
@i{Conforming programs} should not be written using any additional
assumptions about consistency between the run-time
@i{environment} and the startup, evaluation, and compilation
@i{environments}.
Except where noted, when a compile-time and a run-time definition are
different, one of the following occurs at run time:
@table @asis
@item @t{*}
an error of @i{type} @b{error} is signaled
@item @t{*}
the compile-time definition prevails
@item @t{*}
the run-time definition prevails
@end table
If the @i{compiler} processes a @i{function form} whose @i{operator}
is not defined at compile time, no error is signaled at compile time.
@node File Compilation, Literal Objects in Compiled Files, Compilation Semantics, Compilation
@subsection File Compilation
The @i{function} @b{compile-file} performs compilation of
@i{forms} in a file following the rules specified in @ref{Compilation Semantics},
and produces an output file that can be loaded by using @b{load}.
Normally, the @i{top level forms} appearing in a file compiled with
@b{compile-file} are evaluated only when the resulting
compiled file is loaded, and not when the file is compiled. However,
it is typically the case that some forms in the file need to be evaluated
at compile time so the
remainder of the file can be read and compiled correctly.
The @b{eval-when} @i{special form} can be used to control
whether a @i{top level form} is evaluated at compile time, load
time, or both. It is possible to specify any of three situations with
@b{eval-when}, denoted by the symbols @t{:compile-toplevel},
@t{:load-toplevel}, and @t{:execute}. For top level
@b{eval-when} forms, @t{:compile-toplevel} specifies that the
compiler must evaluate the body at compile time, and @t{:load-toplevel} specifies that the compiler must arrange to evaluate
the body at load time. For non-top level @b{eval-when} forms,
@t{:execute} specifies that the body must be executed in the run-time
@i{environment}.
The behavior of this @i{form} can be more precisely understood in
terms of a model of how @b{compile-file} processes forms in
a file to be compiled. There are two processing modes, called
``not-compile-time'' and ``compile-time-too''.
Successive forms are read from the file by @b{compile-file}
and processed in not-compile-time mode; in this mode,
@b{compile-file} arranges for forms to be evaluated only at load time
and not at compile time. When @b{compile-file} is in
compile-time-too mode, forms are evaluated both at compile time and
load time.
@menu
* Processing of Top Level Forms::
* Processing of Defining Macros::
* Constraints on Macros and Compiler Macros::
@end menu
@node Processing of Top Level Forms, Processing of Defining Macros, File Compilation, File Compilation
@subsubsection Processing of Top Level Forms
Processing of @i{top level forms} in the file compiler is defined
as follows:
@table @asis
@item 1.
If the @i{form} is a @i{compiler macro form}
(not disabled by a @b{notinline} @i{declaration}),
the @i{implementation} might or might not choose to compute
the @i{compiler macro expansion} of the @i{form} and,
having performed the expansion, might or might not choose to process the result
as a @i{top level form} in the same processing mode
(compile-time-too or not-compile-time).
If it declines to obtain or use the expansion, it must process the original @i{form}.
@item 2.
If the form is a @i{macro form},
its @i{macro expansion} is computed and processed as a
@i{top level form} in
the same processing mode (compile-time-too or not-compile-time).
@item 3.
If the form is a @b{progn} form, each of its
body @i{forms} is sequentially processed as a
@i{top level form} in the same processing mode.
@item 4.
If the form is a @b{locally},
@b{macrolet}, or @b{symbol-macrolet},
@b{compile-file} establishes the appropriate bindings and processes the
body forms as @i{top level forms} with those bindings in effect
in the same processing mode. (Note that this implies that the lexical
@i{environment} in which @i{top level forms} are processed
is not necessarily the @i{null lexical environment}.)
@item 5.
If the form is an @b{eval-when}
@IRindex{eval-when}
form, it is
handled according to Figure 3--7.
plus .5 fil
\offinterlineskip
@group
@noindent
@w{ @b{CT} @b{LT} @b{E} @b{Mode} @b{Action} @b{New Mode} }
@w{ _________________________________________________}
@w{ Yes Yes --- --- Process compile-time-too }
@w{ No Yes Yes CTT Process compile-time-too }
@w{ No Yes Yes NCT Process not-compile-time }
@w{ No Yes No --- Process not-compile-time }
@w{ Yes No --- --- Evaluate --- }
@w{ No No Yes CTT Evaluate --- }
@w{ No No Yes NCT Discard --- }
@w{ No No No --- Discard --- }
@end group
@w{ Figure 3--7: EVAL-WHEN processing}
Column @b{CT} indicates whether @t{:compile-toplevel} is specified.
Column @b{LT} indicates whether @t{:load-toplevel} is specified.
Column @b{E} indicates whether @t{:execute} is specified.
Column @b{Mode} indicates the processing mode;
a dash (---) indicates that the processing mode is not relevant.
The @b{Action} column specifies one of three actions:
@table @asis
@item @t{}
@b{Process:} process the body as @i{top level forms} in the
specified mode.
@item @t{}
@b{Evaluate:} evaluate the body in the dynamic execution
context of the compiler, using the @i{evaluation environment} as
the global environment and the @i{lexical environment} in which
the @b{eval-when} appears.
@item @t{}
@b{Discard:} ignore the @i{form}.
@end table
The @b{New Mode} column indicates the new processing mode.
A dash (---) indicates the compiler remains in its current mode.
@item 6.
Otherwise, the form is a @i{top level form} that
is not one of the special cases. In compile-time-too mode, the
compiler first evaluates the form in the evaluation
@i{environment} and then minimally compiles it. In not-compile-time
mode, the @i{form} is simply minimally compiled. All @i{subforms}
are treated as @i{non-top-level forms}.
Note that @i{top level forms} are processed in the order in
which they textually appear in the file and that each
@i{top level form} read by the compiler is processed before the next is
read. However, the order of processing (including macro expansion) of
@i{subforms} that are not @i{top level forms} and the order of
further compilation is unspecified as long as Common Lisp semantics
are preserved.
@end table
@b{eval-when} forms cause compile-time evaluation only at
top level. Both @t{:compile-toplevel} and @t{:load-toplevel} situation specifications
are ignored for @i{non-top-level forms}. For @i{non-top-level forms},
an @b{eval-when}
specifying the @t{:execute} situation is treated as an @i{implicit progn}
including the @i{forms} in the body of the @b{eval-when} @i{form};
otherwise, the @i{forms} in the body are ignored.
@node Processing of Defining Macros, Constraints on Macros and Compiler Macros, Processing of Top Level Forms, File Compilation
@subsubsection Processing of Defining Macros
Defining @i{macros} (such as @b{defmacro} or @b{defvar})
appearing within a file being processed by @b{compile-file}
normally have compile-time side effects which affect how subsequent @i{forms}
in the same @i{file} are compiled. A convenient model for explaining how these
side effects happen is that the defining macro expands into one or
more @b{eval-when} @i{forms}, and that the calls which cause the compile-time
side effects to happen appear
in the body of an @t{(eval-when (:compile-toplevel) ...)} @i{form}.
The compile-time side effects may cause information about the definition to
be stored differently than if the defining macro had been processed in the
`normal' way (either interpretively or by loading the compiled file).
In particular, the information stored by the defining @i{macros} at compile time
might or might not be available to the interpreter (either during or after compilation),
or during subsequent calls to the @i{compiler}. For example,
the following code is nonportable because it assumes that the @i{compiler}
stores the macro definition of @t{foo} where it is available to the interpreter:
@example
(defmacro foo (x) `(car ,x))
(eval-when (:execute :compile-toplevel :load-toplevel)
(print (foo '(a b c))))
@end example
A portable way to do the same thing would be to include the macro
definition inside the @b{eval-when} @i{form}, as in:
@example
(eval-when (:execute :compile-toplevel :load-toplevel)
(defmacro foo (x) `(car ,x))
(print (foo '(a b c))))
@end example
Figure 3--8 lists macros that make definitions
available both in the compilation and run-time @i{environments}.
It is not specified whether definitions made available in the
@i{compilation environment} are available in the evaluation
@i{environment}, nor is it specified whether they are available
in subsequent compilation units or subsequent invocations of the
compiler. As with @b{eval-when}, these compile-time side
effects happen only when the defining macros appear at
top level.
@group
@noindent
@w{ declaim define-modify-macro defsetf }
@w{ defclass define-setf-expander defstruct }
@w{ defconstant defmacro deftype }
@w{ define-compiler-macro defpackage defvar }
@w{ define-condition defparameter }
@noindent
@w{ Figure 3--8: Defining Macros That Affect the Compile-Time Environment}
@end group
@node Constraints on Macros and Compiler Macros, , Processing of Defining Macros, File Compilation
@subsubsection Constraints on Macros and Compiler Macros
Except where explicitly stated otherwise, no @i{macro} defined in
the @r{Common Lisp} standard produces an expansion that could cause any of the
@i{subforms} of the @i{macro form} to be treated as
@i{top level forms}. If an @i{implementation} also provides a
@i{special operator} definition of a @r{Common Lisp} @i{macro},
the @i{special operator} definition must be semantically equivalent
in this respect.
@i{Compiler macro} expansions must also have the same
top level evaluation semantics as the @i{form} which they replace.
This is of concern both to @i{conforming implementations} and to
@i{conforming programs}.
@node Literal Objects in Compiled Files, Exceptional Situations in the Compiler, File Compilation, Compilation
@subsection Literal Objects in Compiled Files
The functions @b{eval} and @b{compile} are
required to ensure that @i{literal objects} referenced within the resulting
interpreted or compiled code objects are the @i{same} as the
corresponding @i{objects} in the @i{source code}.
@b{compile-file}, on the other hand,
must produce a @i{compiled file} that, when loaded with
@b{load}, constructs the @i{objects} defined by the
@i{source code} and produces references to them.
In the case of @b{compile-file}, @i{objects}
constructed by @b{load} of the @i{compiled file} cannot be spoken
of as being the @i{same} as the @i{objects} constructed at
compile time, because the @i{compiled file} may be loaded into a different
@i{Lisp image} than the one in which it was compiled. This section
defines the concept of @i{similarity} which relates
@i{objects} in the @i{evaluation environment} to the
corresponding @i{objects} in the @i{run-time environment}.
The constraints on @i{literal objects} described in this section
apply only to @b{compile-file};
@b{eval} and @b{compile} do not copy or coalesce constants.
@menu
* Externalizable Objects::
* Similarity of Literal Objects::
* Similarity of Aggregate Objects::
* Definition of Similarity::
* Extensions to Similarity Rules::
* Additional Constraints on Externalizable Objects::
@end menu
@node Externalizable Objects, Similarity of Literal Objects, Literal Objects in Compiled Files, Literal Objects in Compiled Files
@subsubsection Externalizable Objects
The fact that the @i{file compiler} represents @i{literal} @i{objects}
externally in a @i{compiled file} and must later reconstruct suitable
equivalents of those @i{objects} when that @i{file} is loaded
imposes a need for constraints on the nature of the @i{objects} that can be
used as @i{literal} @i{objects} in @i{code} to be processed
by the @i{file compiler}.
An @i{object} that can be used as a @i{literal} @i{object}
in @i{code} to be processed by the @i{file compiler} is called an
@i{externalizable object}
@IGindex{externalizable object}
.
We define that two @i{objects} are @i{similar}
@IGindex{similar}
if they satisfy
a two-place conceptual equivalence predicate (defined below), which is
independent of the @i{Lisp image} so that the two @i{objects} in
different @i{Lisp images} can be understood to be equivalent under
this predicate. Further, by inspecting the definition of this conceptual
predicate, the programmer can anticipate what aspects of an @i{object}
are reliably preserved by @i{file compilation}.
The @i{file compiler} must cooperate with the @i{loader} in order to
assure that in each case where an @i{externalizable object} is processed
as a @i{literal object}, the @i{loader} will construct a @i{similar}
@i{object}.
The set of @i{objects} that are @i{externalizable objects}
@IGindex{externalizable object}
are those
for which the new conceptual term ``@i{similar}'' is defined, such that
when a @i{compiled file} is @i{loaded}, an @i{object} can be constructed
which can be shown to be @i{similar} to the original @i{object} which
existed at the time the @i{file compiler} was operating.
@node Similarity of Literal Objects, Similarity of Aggregate Objects, Externalizable Objects, Literal Objects in Compiled Files
@subsubsection Similarity of Literal Objects
@node Similarity of Aggregate Objects, Definition of Similarity, Similarity of Literal Objects, Literal Objects in Compiled Files
@subsubsection Similarity of Aggregate Objects
Of the @i{types} over which @i{similarity} is defined,
some are treated as aggregate objects. For these types,
@i{similarity} is defined recursively.
We say that an @i{object} of these types has certain ``basic qualities''
and to satisfy the @i{similarity} relationship, the values of the
corresponding qualities of the two @i{objects} must also be similar.
@node Definition of Similarity, Extensions to Similarity Rules, Similarity of Aggregate Objects, Literal Objects in Compiled Files
@subsubsection Definition of Similarity
Two @i{objects} S (in @i{source code}) and C (in @i{compiled code})
are defined to be @i{similar} if and only if
they are both of one of the @i{types} listed here
(or defined by the @i{implementation})
and they both satisfy all additional requirements of @i{similarity}
indicated for that @i{type}.
@table @asis
@item @b{number}
Two @i{numbers} S and C are @i{similar} if they are of the same @i{type}
and represent the same mathematical value.
@item @b{character}
Two @i{simple} @i{characters} S and C are @i{similar}
if they have @i{similar} @i{code} @i{attributes}.
@i{Implementations} providing additional, @i{implementation-defined}
@i{attributes} must define whether and how @i{non-simple} @i{characters}
can be regarded as @i{similar}.
@item @b{symbol}
Two @i{apparently uninterned} @i{symbols} S and C are @i{similar}
if their
@i{names}
are @i{similar}.
Two @i{interned} symbols S and C are @i{similar}
if their @i{names} are @i{similar},
and if either S is accessible in the @i{current package} at compile time
and C is accessible in the @i{current package} at load time,
or C is accessible in the @i{package} that is @i{similar} to
the @i{home package} of S.
(Note that @i{similarity} of
@i{symbols} is dependent
on neither the @i{current readtable} nor how the @i{function} @b{read} would
parse the @i{characters} in the @i{name} of the @i{symbol}.)
@item @b{package}
Two @i{packages} S and C are @i{similar} if their @i{names} are @i{similar}.
Note that although a @i{package} @i{object} is an @i{externalizable object},
the programmer is responsible for ensuring that the corresponding @i{package} is
already in existence when code referencing it as a @i{literal} @i{object}
is @i{loaded}. The @i{loader} finds the corresponding @i{package} @i{object}
as if by calling @b{find-package} with that @i{name} as an @i{argument}.
An error is signaled by the @i{loader} if no @i{package} exists at load time.
@item @b{random-state}
Two @i{random states} S and C are @i{similar} if S
would always produce the same sequence of pseudo-random numbers
as a @i{copy}_5 of C
when given as the @i{random-state} @i{argument} to the @i{function} @b{random},
assuming equivalent @i{limit} @i{arguments} in each case.
(Note that since C has been processed by the @i{file compiler},
it cannot be used directly as an @i{argument} to @b{random}
because @b{random} would perform a side effect.)
@item @b{cons}
Two @i{conses}, S and C, are @i{similar} if
the @i{car}_2 of S is @i{similar} to the @i{car}_2 of C,
and the @i{cdr}_2 of S is @i{similar} to the @i{cdr}_2 of C.
@item @b{array}
Two one-dimensional @i{arrays}, S and C, are @i{similar} if
the @i{length} of S is @i{similar} to the @i{length} of C,
the @i{actual array element type} of S is @i{similar} to
the @i{actual array element type} of C,
and each @i{active} @i{element} of S is @i{similar} to
the corresponding @i{element} of C.
Two @i{arrays} of @i{rank} other than one, S and C, are @i{similar} if
the @i{rank} of S is @i{similar} to the @i{rank} of C,
each @i{dimension}_1 of S is @i{similar} to
the corresponding @i{dimension}_1 of C,
the @i{actual array element type} of S is @i{similar} to
the @i{actual array element type} of C,
and each @i{element} of S is @i{similar} to
the corresponding @i{element} of C.
In addition,
if S is a @i{simple array}, then C must also be a @i{simple array}.
If S is a @i{displaced array},
has a @i{fill pointer},
or is @i{actually adjustable},
C is permitted to lack any or all of these qualities.
@item @b{hash-table}
Two @i{hash tables} S and C are @i{similar} if they meet the following
three requirements:
@table @asis
@item 1.
They both have the same test
(@i{e.g.}, they are both @b{eql} @i{hash tables}).
@item 2.
There is a unique one-to-one correspondence between the keys of
the two @i{hash tables}, such that the corresponding keys are
@i{similar}.
@item 3.
For all keys, the values associated with two corresponding keys
are @i{similar}.
@end table
If there is more than one possible one-to-one correspondence between
the keys of S and C, the consequences are unspecified.
A @i{conforming program} cannot use a table such as S as an
@i{externalizable constant}.
@item @b{pathname}
Two @i{pathnames} S and C are @i{similar} if all corresponding
@i{pathname components} are @i{similar}.
@item @b{function}
@i{Functions} are not @i{externalizable objects}.
@item @b{structure-object} and @b{standard-object}
A general-purpose concept of @i{similarity} does not exist for @i{structures}
and @i{standard objects}.
However, a @i{conforming program} is permitted to define a @b{make-load-form}
@i{method} for any @i{class} K defined by that @i{program} that is
a @i{subclass} of either @b{structure-object} or @b{standard-object}.
The effect of such a @i{method} is to define that an @i{object} S of @i{type} K
in @i{source code} is @i{similar} to an @i{object} C of @i{type} K
in @i{compiled code} if C was constructed from @i{code} produced by
calling @b{make-load-form} on S.
@end table
@node Extensions to Similarity Rules, Additional Constraints on Externalizable Objects, Definition of Similarity, Literal Objects in Compiled Files
@subsubsection Extensions to Similarity Rules
Some @i{objects}, such as @i{streams}, @b{readtables}, and @b{methods}
are not @i{externalizable objects} under the definition of similarity given above.
That is, such @i{objects} may not portably appear as @i{literal} @i{objects}
in @i{code} to be processed by the @i{file compiler}.
An @i{implementation} is permitted to extend the rules of similarity,
so that other kinds of @i{objects} are @i{externalizable objects}
for that @i{implementation}.
If for some kind of @i{object}, @i{similarity} is
neither defined by this specification
nor by the @i{implementation},
then the @i{file compiler} must signal an error upon encountering such
an @i{object} as a @i{literal constant}.
@node Additional Constraints on Externalizable Objects, , Extensions to Similarity Rules, Literal Objects in Compiled Files
@subsubsection Additional Constraints on Externalizable Objects
If two @i{literal objects} appearing in the source code for a single file
processed with
the @i{file compiler}
are the @i{identical},
the corresponding @i{objects} in the @i{compiled code}
must also be the @i{identical}.
With the exception of @i{symbols} and @i{packages}, any two
@i{literal objects}
in @i{code} being processed by
the @i{file compiler}
may be @i{coalesced}
if and only if they are @i{similar};
if they are either both @i{symbols} or both @i{packages},
they may only be @i{coalesced} if and only if they are @i{identical}.
@i{Objects} containing circular references can
be @i{externalizable objects}.
The @i{file compiler} is required to preserve @b{eql}ness of
substructures within a @i{file}.
Preserving @b{eql}ness means that subobjects that are
the @i{same}
in the @i{source code} must
be
the @i{same}
in the corresponding @i{compiled code}.
In addition, the following are constraints on the handling of
@i{literal objects} by the @i{file compiler}:
@table @asis
@item @t{}
@b{array:} If an @i{array} in the source code is a
@i{simple array}, then the corresponding @i{array}
in the compiled code will also be a @i{simple array}. If
an @i{array} in the source code is displaced, has a
@i{fill pointer}, or is @i{actually adjustable}, the corresponding
@i{array} in the compiled code might lack any or all of these
qualities. If an @i{array} in the source code has a fill
pointer, then the corresponding @i{array} in the compiled
code might be only the size implied by the fill pointer.
@item @t{}
@b{packages:} The loader is required to find the
corresponding @i{package} @i{object} as if by calling
@b{find-package} with the package name as an argument.
An error of @i{type} @b{package-error} is signaled if no
@i{package} of that name exists at load time.
@item @t{}
@b{random-state:} A constant @i{random state}
object cannot be used as the state argument
to the @i{function} @b{random} because @b{random} modifies this data structure.
@item @t{}
@b{structure, standard-object:}
@i{Objects} of @i{type} @b{structure-object} and @b{standard-object}
may appear in compiled constants if there is an
appropriate @b{make-load-form} method defined for that
@i{type}.
The @i{file compiler} calls @b{make-load-form} on any @i{object}
that is referenced as a @i{literal object} if the @i{object} is a
@i{generalized instance} of @b{standard-object},
@b{structure-object}, @b{condition}, or any of a
(possibly empty) @i{implementation-dependent} set of other @i{classes}.
The @i{file compiler} only calls @b{make-load-form} once for
any given @i{object} within a single @i{file}.
@item @t{}
@b{symbol:} In order to guarantee that @i{compiled files} can be @i{loaded}
correctly, users must ensure that the @i{packages} referenced in those @i{files}
are defined consistently at compile time and load time. @i{Conforming programs}
must satisfy the following requirements:
@table @asis
@item 1.
The @i{current package} when a @i{top level form} in the @i{file}
is processed by @b{compile-file} must be the same as the @i{current package}
when the @i{code} corresponding to that @i{top level form} in the
@i{compiled file} is executed by @b{load}. In particular:
@table @asis
@item a.
Any @i{top level form} in a @i{file} that alters
the @i{current package} must change it to a @i{package}
of the same @i{name} both at compile time and at load time.
@item b.
If the first @i{non-atomic} @i{top level form} in the @i{file}
is not an @b{in-package} @i{form}, then the @i{current package}
at the time @b{load} is called must be a @i{package} with the
same @i{name} as the package that was the @i{current package}
at the time @b{compile-file} was called.
@end table
@item 2.
For all @i{symbols}
appearing lexically within a @i{top level form} that
were @i{accessible} in the @i{package} that was the @i{current package}
during processing of that @i{top level form} at compile time, but
whose @i{home package} was another @i{package}, at load time there must
be a @i{symbol} with the same @i{name} that is @i{accessible} in both the
load-time @i{current package} and in the @i{package}
with the same @i{name} as the
compile-time @i{home package}.
@item 3.
For all @i{symbols} represented in the @i{compiled file}
that were @i{external symbols} in
their @i{home package} at compile time, there must be a @i{symbol} with the
same @i{name} that is an @i{external symbol} in the @i{package}
with the same @i{name} at load time.
@end table
If any of these conditions do not hold, the @i{package} in which the @i{loader} looks
for the affected @i{symbols} is unspecified. @i{Implementations} are permitted
to signal an error or to define this behavior.
@end table
@node Exceptional Situations in the Compiler, , Literal Objects in Compiled Files, Compilation
@subsection Exceptional Situations in the Compiler
@b{compile} and @b{compile-file} are permitted to
signal errors and warnings, including errors due to compile-time
processing of @t{(eval-when (:compile-toplevel) ...)} forms,
macro expansion, and conditions signaled by the compiler itself.
@i{Conditions} of @i{type} @b{error} might be signaled by the compiler
in situations where the compilation cannot proceed without intervention.
In addition to situations for which the standard specifies that
@i{conditions} of @i{type} @b{warning} must or might be signaled,
warnings might be signaled in situations where the compiler can
determine that the consequences are undefined or that a run-time
error will be signaled. Examples of this situation are as follows:
violating type declarations,
altering or assigning the value of a constant defined with @b{defconstant},
calling built-in Lisp functions with a wrong number of arguments or malformed keyword
argument lists,
and using unrecognized declaration specifiers.
The compiler is permitted to issue warnings about matters of
programming style as conditions of @i{type} @b{style-warning}.
Examples of this situation are as follows:
redefining a function using a different argument list,
calling a function with a wrong number of arguments,
not declaring @b{ignore} of a local variable that is not referenced,
and referencing a variable declared @b{ignore}.
Both @b{compile} and @b{compile-file} are permitted
(but not required) to @i{establish} a @i{handler}
for @i{conditions} of @i{type} @b{error}. For example, they
might signal a warning, and restart compilation from some
@i{implementation-dependent} point in order to let the
compilation proceed without manual intervention.
Both @b{compile} and @b{compile-file} return three
values, the second two indicating whether the source code being compiled
contained errors and whether style warnings were issued.
Some warnings might be deferred until the end of compilation.
See @b{with-compilation-unit}.
@c end of including concept-compile
@node Declarations, Lambda Lists, Compilation, Evaluation and Compilation
@section Declarations
@c including concept-decls
@i{Declarations}
@IGindex{declaration}
provide a way of specifying information for use by
program processors, such as the evaluator or the compiler.
@i{Local declarations}
@IGindex{local declaration}
can be embedded in executable code using @b{declare}.
@i{Global declarations}
@IGindex{global declaration}
,
or @i{proclamations}
@IGindex{proclamation}
,
are established by @b{proclaim} or @b{declaim}.
The @b{the} @i{special form} provides a shorthand notation for
making a @i{local declaration} about the @i{type} of the
@i{value} of a given @i{form}.
The consequences are undefined if a program violates a @i{declaration}
or a @i{proclamation}.
@menu
* Minimal Declaration Processing Requirements::
* Declaration Specifiers::
* Declaration Identifiers::
* Declaration Scope::
@end menu
@node Minimal Declaration Processing Requirements, Declaration Specifiers, Declarations, Declarations
@subsection Minimal Declaration Processing Requirements
In general, an @i{implementation} is free to ignore
@i{declaration specifiers} except for the
@b{declaration}
@IRindex{declaration}
,
@b{notinline}
@IRindex{notinline}
,
@b{safety}
@IRindex{safety}
,
and @b{special}
@IRindex{special}
@i{declaration specifiers}.
A @b{declaration} @i{declaration} must suppress warnings
about unrecognized @i{declarations} of the kind that it declares.
If an @i{implementation} does not produce warnings about
unrecognized declarations, it may safely ignore this @i{declaration}.
A @b{notinline} @i{declaration} must be recognized by any @i{implementation}
that supports inline functions or @i{compiler macros} in order to disable those facilities.
An @i{implementation} that does not use inline functions or @i{compiler macros}
may safely ignore this @i{declaration}.
A @b{safety} @i{declaration} that increases the current safety level
must always be recognized. An @i{implementation} that always processes
code as if safety were high may safely ignore this @i{declaration}.
A @b{special} @i{declaration} must be processed by all @i{implementations}.
@node Declaration Specifiers, Declaration Identifiers, Minimal Declaration Processing Requirements, Declarations
@subsection Declaration Specifiers
A @i{declaration specifier}
@IGindex{declaration specifier}
is an @i{expression} that can appear at
top level of a @b{declare} expression or a @b{declaim} form, or as
the argument to @b{proclaim}.
It is a @i{list} whose @i{car} is a @i{declaration identifier},
and whose @i{cdr} is data interpreted according to rules specific to
the @i{declaration identifier}.
@node Declaration Identifiers, Declaration Scope, Declaration Specifiers, Declarations
@subsection Declaration Identifiers
Figure 3--9 shows a list of all
@i{declaration identifiers}
@IGindex{declaration identifier}
defined by this standard.
@group
@noindent
@w{ declaration ignore special }
@w{ dynamic-extent inline type }
@w{ ftype notinline }
@w{ ignorable optimize }
@noindent
@w{ Figure 3--9: Common Lisp Declaration Identifiers}
@end group
An implementation is free to support other (@i{implementation-defined})
@i{declaration identifiers} as well.
A warning might be issued
if a @i{declaration identifier}
is not among those defined above,
is not defined by the @i{implementation},
is not a @i{type} @i{name},
and has not been declared in a @b{declaration} @i{proclamation}.
@menu
* Shorthand notation for Type Declarations::
@end menu
@node Shorthand notation for Type Declarations, , Declaration Identifiers, Declaration Identifiers
@subsubsection Shorthand notation for Type Declarations
A @i{type specifier} can be used as a @i{declaration identifier}.
@t{(@i{type-specifier} @{@i{var}@}{*})} is taken as shorthand for
@t{(type @i{type-specifier} @{@i{var}@}{*})}.
@node Declaration Scope, , Declaration Identifiers, Declarations
@subsection Declaration Scope
@i{Declarations} can be divided into two kinds: those that apply to the
@i{bindings} of @i{variables} or @i{functions}; and those that
do not apply to @i{bindings}.
A @i{declaration} that appears at the head of a binding @i{form}
and applies to a @i{variable} or @i{function} @i{binding}
made by that @i{form} is called a @i{bound declaration}
@IGindex{bound declaration}
;
such a @i{declaration} affects both the @i{binding} and
any references within the @i{scope} of the @i{declaration}.
@i{Declarations} that are not @i{bound declarations} are called
@i{free declarations}
@IGindex{free declaration}
.
A @i{free declaration} in a @i{form} F1 that applies to a @i{binding}
for a @i{name} N @i{established} by some @i{form} F2
of which F1 is a @i{subform}
affects only references to N within F1; it does not to apply to
other references to N outside of F1, nor does it affect the manner
in which the @i{binding} of N by F2 is @i{established}.
@i{Declarations} that do not apply to @i{bindings} can only appear
as @i{free declarations}.
The @i{scope} of a @i{bound declaration} is the same as the
@i{lexical scope}
of the @i{binding} to which it applies;
for @i{special variables},
this means the @i{scope} that the @i{binding}
would have had had it been a @i{lexical binding}.
Unless explicitly stated otherwise, the @i{scope} of a
@i{free declaration} includes only the body @i{subforms} of
the @i{form} at whose head it appears, and no other @i{subforms}.
The @i{scope} of @i{free declarations} specifically does not
include @i{initialization forms} for @i{bindings} established
by the @i{form} containing the @i{declarations}.
Some @i{iteration forms} include step, end-test, or result
@i{subforms} that are also included in the @i{scope}
of @i{declarations} that appear in the @i{iteration form}.
Specifically, the @i{iteration forms} and @i{subforms} involved
are:
@table @asis
@item @t{*}
@b{do}, @b{do*}:
@i{step-forms}, @i{end-test-form}, and @i{result-forms}.
@item @t{*}
@b{dolist}, @b{dotimes}:
@i{result-form}
@item @t{*}
@b{do-all-symbols}, @b{do-external-symbols}, @b{do-symbols}:
@i{result-form}
@end table
@menu
* Examples of Declaration Scope::
@end menu
@node Examples of Declaration Scope, , Declaration Scope, Declaration Scope
@subsubsection Examples of Declaration Scope
Here is an example illustrating the @i{scope} of @i{bound declarations}.
@example
(let ((x 1)) ;[1] 1st occurrence of x
(declare (special x)) ;[2] 2nd occurrence of x
(let ((x 2)) ;[3] 3rd occurrence of x
(let ((old-x x) ;[4] 4th occurrence of x
(x 3)) ;[5] 5th occurrence of x
(declare (special x)) ;[6] 6th occurrence of x
(list old-x x)))) ;[7] 7th occurrence of x
@result{} (2 3)
@end example
The first occurrence of @t{x} @i{establishes} a @i{dynamic binding}
of @t{x} because of the @b{special} @i{declaration} for @t{x}
in the second line. The third occurrence of @t{x} @i{establishes} a
@i{lexical binding} of @t{x} (because there is no @b{special}
@i{declaration} in the corresponding @b{let} @i{form}).
The fourth occurrence of @t{x} @i{x} is a reference to the
@i{lexical binding} of @t{x} established in the third line.
The fifth occurrence of @t{x} @i{establishes} a @i{dynamic binding}
of @i{x} for the body of the @b{let} @i{form} that begins on
that line because of the @b{special} @i{declaration} for @t{x}
in the sixth line. The reference to @t{x} in the fourth line is not
affected by the @b{special} @i{declaration} in the sixth line
because that reference is not within the ``would-be @i{lexical scope}''
of the @i{variable} @t{x} in the fifth line. The reference to @t{x}
in the seventh line is a reference to the @i{dynamic binding} of @i{x}
@i{established} in the fifth line.
Here is another example, to illustrate the @i{scope} of a
@i{free declaration}. In the following:
@example
(lambda (&optional (x (foo 1))) ;[1]
(declare (notinline foo)) ;[2]
(foo x)) ;[3]
@end example
the @i{call} to @t{foo} in the first line might be
compiled inline even though the @i{call} to @t{foo} in
the third line must not be. This is because
the @b{notinline} @i{declaration}
for @t{foo} in the second line applies only to the body on the
third line. In order to suppress inlining for both @i{calls},
one might write:
@example
(locally (declare (notinline foo)) ;[1]
(lambda (&optional (x (foo 1))) ;[2]
(foo x))) ;[3]
@end example
or, alternatively:
@example
(lambda (&optional ;[1]
(x (locally (declare (notinline foo)) ;[2]
(foo 1)))) ;[3]
(declare (notinline foo)) ;[4]
(foo x)) ;[5]
@end example
Finally, here is an example that shows the @i{scope} of
@i{declarations} in an @i{iteration form}.
@example
(let ((x 1)) ;[1]
(declare (special x)) ;[2]
(let ((x 2)) ;[3]
(dotimes (i x x) ;[4]
(declare (special x))))) ;[5]
@result{} 1
@end example
In this example, the first reference to @t{x} on the fourth line is to
the @i{lexical binding} of @t{x} established on the third line.
However, the second occurrence of @t{x} on the fourth line lies within
the @i{scope} of the @i{free declaration} on the fifth line
(because this is the @i{result-form} of the @b{dotimes})
and therefore refers to the @i{dynamic binding} of @t{x}.
@c end of including concept-decls
@node Lambda Lists, Error Checking in Function Calls, Declarations, Evaluation and Compilation
@section Lambda Lists
@c including concept-bvl
A @i{lambda list}
@IGindex{lambda list}
is a @i{list} that
specifies a set of @i{parameters} (sometimes called @i{lambda variables})
and a protocol for receiving @i{values} for those @i{parameters}.
There are several kinds of @i{lambda lists}.
@group
@noindent
@w{ Context Kind of Lambda List }
@w{ @b{defun} @i{form} @i{ordinary lambda list} }
@w{ @b{defmacro} @i{form} @i{macro lambda list} }
@w{ @i{lambda expression} @i{ordinary lambda list} }
@w{ @b{flet} local @i{function} definition @i{ordinary lambda list} }
@w{ @b{labels} local @i{function} definition @i{ordinary lambda list} }
@w{ @b{handler-case} @i{clause} specification @i{ordinary lambda list} }
@w{ @b{restart-case} @i{clause} specification @i{ordinary lambda list} }
@w{ @b{macrolet} local @i{macro} definition @i{macro lambda list} }
@w{ @b{define-method-combination} @i{ordinary lambda list} }
@w{ @b{define-method-combination} @t{:arguments} option @i{define-method-combination arguments lambda list} }
@w{ @b{defstruct} @t{:constructor} option @i{boa lambda list} }
@w{ @b{defgeneric} @i{form} @i{generic function lambda list} }
@w{ @b{defgeneric} @i{method} clause @i{specialized lambda list} }
@w{ @b{defmethod} @i{form} @i{specialized lambda list} }
@w{ @b{defsetf} @i{form} @i{defsetf lambda list} }
@w{ @b{define-setf-expander} @i{form} @i{macro lambda list} }
@w{ @b{deftype} @i{form} @i{deftype lambda list} }
@w{ @b{destructuring-bind} @i{form} @i{destructuring lambda list} }
@w{ @b{define-compiler-macro} @i{form} @i{macro lambda list} }
@w{ @b{define-modify-macro} @i{form} @i{define-modify-macro lambda list} }
@noindent
@w{ Figure 3--10: What Kind of Lambda Lists to Use }
@end group
Figure 3--11 lists some @i{defined names} that are applicable
to @i{lambda lists}.
@group
@noindent
@w{ lambda-list-keywords lambda-parameters-limit }
@noindent
@w{ Figure 3--11: Defined names applicable to lambda lists}
@end group
@menu
* Ordinary Lambda Lists::
* Generic Function Lambda Lists::
* Specialized Lambda Lists::
* Macro Lambda Lists::
* Destructuring Lambda Lists::
* Boa Lambda Lists::
* Defsetf Lambda Lists::
* Deftype Lambda Lists::
* Define-modify-macro Lambda Lists::
* Define-method-combination Arguments Lambda Lists::
* Syntactic Interaction of Documentation Strings and Declarations::
@end menu
@node Ordinary Lambda Lists, Generic Function Lambda Lists, Lambda Lists, Lambda Lists
@subsection Ordinary Lambda Lists
An @i{ordinary lambda list}
@IGindex{ordinary lambda list}
is used to describe how a set of
@i{arguments} is received by an @i{ordinary} @i{function}.
The @i{defined names} in Figure 3--12 are those which use
@i{ordinary lambda lists}:
@group
@noindent
@w{ define-method-combination handler-case restart-case }
@w{ defun labels }
@w{ flet lambda }
@noindent
@w{ Figure 3--12: Standardized Operators that use Ordinary Lambda Lists}
@end group
An @i{ordinary lambda list} can contain the @i{lambda list keywords} shown
in Figure 3--13.
@group
@noindent
@w{ @b{&allow-other-keys} @b{&key} @b{&rest} }
@w{ @b{&aux} @b{&optional} }
@noindent
@w{ Figure 3--13: Lambda List Keywords used by Ordinary Lambda Lists}
@end group
Each @i{element} of a @i{lambda list} is either a parameter specifier
or a @i{lambda list keyword}.
Implementations are free to provide additional @i{lambda list keywords}.
For a list of all @i{lambda list keywords}
used by the implementation, see @b{lambda-list-keywords}.
The syntax for @i{ordinary lambda lists} is as follows:
@w{@i{lambda-list} ::=@r{(}@{@i{var}@}{*}}
@w{ @t{[}{&optional} @{@i{var} |
@r{(}@i{var} @r{[}init-form @r{[}supplied-p-parameter@r{]}@r{]}@r{)}@}{*}@t{]}}
@w{ @t{[}{&rest} @i{var}@t{]}}
@w{ @t{[}{&key} @{@i{var} |
@r{(}@{@i{var} |
@r{(}@i{keyword-name} @i{var}@r{)}@}
@r{[}init-form @r{[}supplied-p-parameter@r{]}@r{]}@r{)}@}{*} pt @r{[}@t{&allow-other-keys}@r{]}@t{]}}
@w{ @t{[}{&aux} @{@i{var} | @r{(}@i{var} @r{[}@i{init-form}@r{]}@r{)}@}{*}@t{]}@r{)}}
@w{ }
A @i{var} or @i{supplied-p-parameter} must be a @i{symbol}
that is not the name of a @i{constant variable}.
An @i{init-form} can be any @i{form}.
Whenever any @i{init-form} is evaluated for any parameter
specifier, that @i{form} may refer to any parameter variable to
the left of the specifier in which the @i{init-form} appears,
including any @i{supplied-p-parameter} variables, and may rely
on the fact that no other parameter variable has yet been bound
(including its own parameter variable).
A @i{keyword-name} can be any @i{symbol},
but by convention is normally a @i{keyword}_1;
all @i{standardized} @i{functions} follow that convention.
An @i{ordinary lambda list} has five parts, any or all of which may be empty.
For information about the treatment of argument mismatches,
see @ref{Error Checking in Function Calls}.
@menu
* Specifiers for the required parameters::
* Specifiers for optional parameters::
* A specifier for a rest parameter::
* Specifiers for keyword parameters::
* Suppressing Keyword Argument Checking::
* Examples of Suppressing Keyword Argument Checking::
* Specifiers for @b{&aux} variables::
* Examples of Ordinary Lambda Lists::
@end menu
@node Specifiers for the required parameters, Specifiers for optional parameters, Ordinary Lambda Lists, Ordinary Lambda Lists
@subsubsection Specifiers for the required parameters
These are all the parameter specifiers up to
the first @i{lambda list keyword};
if there are no @i{lambda list keywords},
then all the specifiers are for required parameters.
Each required parameter is specified by a parameter variable @i{var}.
@i{var} is bound as a lexical variable unless it is declared @b{special}.
If there are @t{n} required parameters (@t{n} may be zero),
there must be at least @t{n} passed arguments, and the
required parameters are bound to the first @t{n} passed arguments;
see @ref{Error Checking in Function Calls}.
The other parameters are then processed using any remaining arguments.
@node Specifiers for optional parameters, A specifier for a rest parameter, Specifiers for the required parameters, Ordinary Lambda Lists
@subsubsection Specifiers for optional parameters
@IRindex{&optional}
If @b{&optional} is present,
the optional parameter specifiers are those following
@b{&optional}
up to the next @i{lambda list keyword} or the end of the list.
If optional parameters are specified, then each one is processed as
follows. If any unprocessed arguments remain, then the parameter variable
@i{var} is bound to the next remaining argument, just as for a required
parameter. If no arguments remain, however, then @i{init-form}
is evaluated, and the parameter variable
is bound to the resulting value
(or to @b{nil} if no @i{init-form} appears
in the parameter specifier).
If another variable name @i{supplied-p-parameter}
appears in the specifier, it is bound
to @i{true} if an argument had been available, and to @i{false} if no
argument remained (and therefore @i{init-form} had to be evaluated).
@i{Supplied-p-parameter}
is bound not to an argument but to a value indicating whether or not
an argument had been supplied for the corresponding @i{var}.
@node A specifier for a rest parameter, Specifiers for keyword parameters, Specifiers for optional parameters, Ordinary Lambda Lists
@subsubsection A specifier for a rest parameter
@IRindex{&rest}
@b{&rest}, if present, must be followed by a single @i{rest parameter}
specifier, which in turn must be followed by another
@i{lambda list keyword} or the end of the @i{lambda list}. After all
optional parameter specifiers have been processed, then there may or
may not be a @i{rest parameter}. If there is a @i{rest parameter}, it is
bound to a @i{list} of all as-yet-unprocessed arguments. If
no unprocessed arguments remain, the @i{rest parameter} is bound to the
@i{empty list}. If there is no @i{rest parameter} and there are no
@i{keyword parameters}, then an error
should be signaled if
any unprocessed arguments remain; see @ref{Error Checking in Function Calls}.
The value of a @i{rest parameter}
is permitted, but not required, to share structure with the
last argument to @b{apply}.
@IRindex{&key}
@IRindex{&allow-other-keys}
@node Specifiers for keyword parameters, Suppressing Keyword Argument Checking, A specifier for a rest parameter, Ordinary Lambda Lists
@subsubsection Specifiers for keyword parameters
If @b{&key}
is present, all specifiers up to the next @i{lambda list keyword}
or the end of the @i{list} are keyword parameter specifiers.
When keyword parameters are processed,
the same arguments are processed that
would be made into a @i{list} for a @i{rest parameter}.
It is permitted to specify both @b{&rest} and @b{&key}.
In this case the remaining arguments are used for both purposes;
that is, all remaining arguments are made into a @i{list} for the
@i{rest parameter}, and are also processed for the @b{&key} parameters.
If @b{&key} is specified, there must remain
an even number of arguments; see @ref{Odd Number of Keyword Arguments}.
These arguments are considered as pairs,
the first argument in each pair being interpreted as a name
and the second as the corresponding value.
The first @i{object} of each pair must be a @i{symbol};
see @ref{Invalid Keyword Arguments}.
The keyword parameter specifiers may optionally be followed by the
@i{lambda list keyword} @b{&allow-other-keys}.
In each keyword parameter specifier must be a name @i{var} for
the parameter variable.
If the @i{var} appears alone or in a @t{(@i{var} @i{init-form})}
combination, the keyword name used when matching @i{arguments} to @i{parameters}
is a @i{symbol} in the @t{KEYWORD} @i{package} whose @i{name} is the
@i{same} (under @b{string=}) as @i{var}'s.
If the notation @t{((@i{keyword-name} @i{var}) @i{init-form})} is used,
then the keyword name used to match @i{arguments} to @i{parameters} is
@i{keyword-name}, which may be a @i{symbol} in any @i{package}.
(Of course, if it is not a @i{symbol} in the @t{KEYWORD} @i{package},
it does not necessarily self-evaluate, so care must be taken when calling the function
to make sure that normal evaluation still yields the keyword name.)
Thus
@example
(defun foo (&key radix (type 'integer)) ...)
@end example
means exactly the same as
@example
(defun foo (&key ((:radix radix)) ((:type type) 'integer)) ...)
@end example
The keyword parameter specifiers are, like all parameter specifiers,
effectively processed from left to right. For each keyword parameter
specifier, if there is an argument pair whose name matches that
specifier's name (that is, the names are @b{eq}), then the
parameter variable for that specifier is bound to the second item (the
value) of that argument pair. If more than one such argument pair
matches, the leftmost argument pair is used. If no such argument pair
exists, then the @i{init-form} for that specifier is evaluated and
the parameter variable is bound to that value (or to @b{nil} if no
@i{init-form} was specified). @i{supplied-p-parameter} is
treated as for @b{&optional} parameters: it is bound to @i{true} if there
was a matching argument pair, and to @i{false} otherwise.
Unless keyword argument checking is suppressed,
an argument pair must a name matched by a parameter specifier;
see @ref{Unrecognized Keyword Arguments}.
If keyword argument checking is suppressed,
then it is permitted for an argument pair
to match no parameter specifier, and the argument pair is ignored, but
such an argument pair is accessible through the @i{rest parameter} if
one was supplied. The purpose of these mechanisms is to allow sharing
of argument lists among several @i{lambda expressions} and to
allow either the caller or the called @i{lambda expression} to
specify that such sharing may be taking place.
Note that if @b{&key} is present, a keyword argument of @t{:allow-other-keys}
is always permitted---regardless of whether the associated value is @i{true}
or @i{false}. However, if the value is @i{false}, other non-matching
keywords are not tolerated (unless @b{&allow-other-keys} was used).
Furthermore, if the receiving argument list specifies a regular argument which
would be flagged by @t{:allow-other-keys}, then @t{:allow-other-keys} has both
its special-cased meaning (identifying whether additional keywords are permitted)
and its normal meaning (data flow into the function in question).
@node Suppressing Keyword Argument Checking, Examples of Suppressing Keyword Argument Checking, Specifiers for keyword parameters, Ordinary Lambda Lists
@subsubsection Suppressing Keyword Argument Checking
If @b{&allow-other-keys} was specified in the @i{lambda list} of a @i{function},
@i{keyword}_2 @i{argument} checking is suppressed in calls
to that @i{function}.
If the @t{:allow-other-keys} @i{argument} is @i{true} in a call to a @i{function},
@i{keyword}_2 @i{argument} checking is suppressed
in that call.
The @t{:allow-other-keys} @i{argument} is permissible in all situations involving
@i{keyword}_2 @i{arguments}, even when its associated @i{value}
is @i{false}.
@node Examples of Suppressing Keyword Argument Checking, Specifiers for @b{&aux} variables, Suppressing Keyword Argument Checking, Ordinary Lambda Lists
@subsubsection Examples of Suppressing Keyword Argument Checking
@example
;;; The caller can supply :ALLOW-OTHER-KEYS T to suppress checking.
((lambda (&key x) x) :x 1 :y 2 :allow-other-keys t) @result{} 1
;;; The callee can use &ALLOW-OTHER-KEYS to suppress checking.
((lambda (&key x &allow-other-keys) x) :x 1 :y 2) @result{} 1
;;; :ALLOW-OTHER-KEYS NIL is always permitted.
((lambda (&key) t) :allow-other-keys nil) @result{} T
;;; As with other keyword arguments, only the left-most pair
;;; named :ALLOW-OTHER-KEYS has any effect.
((lambda (&key x) x)
:x 1 :y 2 :allow-other-keys t :allow-other-keys nil)
@result{} 1
;;; Only the left-most pair named :ALLOW-OTHER-KEYS has any effect,
;;; so in safe code this signals a PROGRAM-ERROR (and might enter the
;;; debugger). In unsafe code, the consequences are undefined.
((lambda (&key x) x) ;This call is not valid
:x 1 :y 2 :allow-other-keys nil :allow-other-keys t)
@end example
@node Specifiers for @b{&aux} variables, Examples of Ordinary Lambda Lists, Examples of Suppressing Keyword Argument Checking, Ordinary Lambda Lists
@subsubsection Specifiers for @b{&aux} variables
@IRindex{&aux}
These are not really parameters. If the @i{lambda list keyword}
@b{&aux} is present, all specifiers after it are auxiliary variable
specifiers. After all parameter specifiers have been processed, the
auxiliary variable specifiers (those following {&aux}) are processed
from left to right. For each one, @i{init-form} is evaluated and
@i{var} is bound to that value (or to @b{nil} if no @i{init-form}
was specified). @b{&aux} variable processing is analogous to
@b{let*} processing.
@example
(lambda (x y &aux (a (car x)) (b 2) c) (list x y a b c))
@equiv{} (lambda (x y) (let* ((a (car x)) (b 2) c) (list x y a b c)))
@end example
@node Examples of Ordinary Lambda Lists, , Specifiers for @b{&aux} variables, Ordinary Lambda Lists
@subsubsection Examples of Ordinary Lambda Lists
Here are some examples involving @i{optional parameters} and @i{rest parameters}:
@example
((lambda (a b) (+ a (* b 3))) 4 5) @result{} 19
((lambda (a &optional (b 2)) (+ a (* b 3))) 4 5) @result{} 19
((lambda (a &optional (b 2)) (+ a (* b 3))) 4) @result{} 10
((lambda (&optional (a 2 b) (c 3 d) &rest x) (list a b c d x)))
@result{} (2 NIL 3 NIL NIL)
((lambda (&optional (a 2 b) (c 3 d) &rest x) (list a b c d x)) 6)
@result{} (6 T 3 NIL NIL)
((lambda (&optional (a 2 b) (c 3 d) &rest x) (list a b c d x)) 6 3)
@result{} (6 T 3 T NIL)
((lambda (&optional (a 2 b) (c 3 d) &rest x) (list a b c d x)) 6 3 8)
@result{} (6 T 3 T (8))
((lambda (&optional (a 2 b) (c 3 d) &rest x) (list a b c d x))
6 3 8 9 10 11)
@result{} (6 t 3 t (8 9 10 11))
@end example
Here are some examples involving @i{keyword parameters}:
@example
((lambda (a b &key c d) (list a b c d)) 1 2) @result{} (1 2 NIL NIL)
((lambda (a b &key c d) (list a b c d)) 1 2 :c 6) @result{} (1 2 6 NIL)
((lambda (a b &key c d) (list a b c d)) 1 2 :d 8) @result{} (1 2 NIL 8)
((lambda (a b &key c d) (list a b c d)) 1 2 :c 6 :d 8) @result{} (1 2 6 8)
((lambda (a b &key c d) (list a b c d)) 1 2 :d 8 :c 6) @result{} (1 2 6 8)
((lambda (a b &key c d) (list a b c d)) :a 1 :d 8 :c 6) @result{} (:a 1 6 8)
((lambda (a b &key c d) (list a b c d)) :a :b :c :d) @result{} (:a :b :d NIL)
((lambda (a b &key ((:sea c)) d) (list a b c d)) 1 2 :sea 6) @result{} (1 2 6 NIL)
((lambda (a b &key ((c c)) d) (list a b c d)) 1 2 'c 6) @result{} (1 2 6 NIL)
@end example
Here are some examples involving @i{optional parameters}, @i{rest parameters},
and @i{keyword parameters} together:
@example
((lambda (a &optional (b 3) &rest x &key c (d a))
(list a b c d x)) 1)
@result{} (1 3 NIL 1 ())
((lambda (a &optional (b 3) &rest x &key c (d a))
(list a b c d x)) 1 2)
@result{} (1 2 NIL 1 ())
((lambda (a &optional (b 3) &rest x &key c (d a))
(list a b c d x)) :c 7)
@result{} (:c 7 NIL :c ())
((lambda (a &optional (b 3) &rest x &key c (d a))
(list a b c d x)) 1 6 :c 7)
@result{} (1 6 7 1 (:c 7))
((lambda (a &optional (b 3) &rest x &key c (d a))
(list a b c d x)) 1 6 :d 8)
@result{} (1 6 NIL 8 (:d 8))
((lambda (a &optional (b 3) &rest x &key c (d a))
(list a b c d x)) 1 6 :d 8 :c 9 :d 10)
@result{} (1 6 9 8 (:d 8 :c 9 :d 10))
@end example
As an example of the use of @b{&allow-other-keys} and
@t{:allow-other-keys}, consider a @i{function} that takes two named
arguments of its own and also accepts additional named arguments to be
passed to @b{make-array}:
@example
(defun array-of-strings (str dims &rest named-pairs
&key (start 0) end &allow-other-keys)
(apply #'make-array dims
:initial-element (subseq str start end)
:allow-other-keys t
named-pairs))
@end example
This @i{function} takes a @i{string} and dimensioning
information and returns an @i{array} of the specified
dimensions, each of whose elements is the specified
@i{string}. However, @t{:start} and @t{:end} named
arguments may be used to specify that a substring of the given
@i{string} should be used. In addition, the presence of
@b{&allow-other-keys} in the @i{lambda list} indicates that the
caller may supply additional named arguments; the @i{rest parameter}
provides access to them. These additional named arguments are passed
to @b{make-array}. The @i{function} @b{make-array}
normally does not allow the named arguments @t{:start}
and @t{:end} to be used, and an error should be
signaled if such named arguments are supplied to @b{make-array}.
However, the presence in the call to @b{make-array}
of the named argument @t{:allow-other-keys} with
a @i{true} value causes any extraneous named arguments, including
@t{:start} and @t{:end}, to be acceptable and ignored.
@node Generic Function Lambda Lists, Specialized Lambda Lists, Ordinary Lambda Lists, Lambda Lists
@subsection Generic Function Lambda Lists
A @i{generic function lambda list}
@IGindex{generic function lambda list}
is used to describe the overall shape of
the argument list to be accepted by a @i{generic function}.
Individual @i{method} @i{signatures} might contribute additional
@i{keyword parameters} to the @i{lambda list} of the @i{effective method}.
A @i{generic function lambda list} is used by @b{defgeneric}.
A @i{generic function lambda list} has the following syntax:
@w{@i{lambda-list} ::=@r{(}@{@i{var}@}{*}}
@w{ @t{[}{&optional} @{@i{var} | @r{(}@i{var}@r{)}@}{*}@t{]}}
@w{ @t{[}{&rest} @i{var}@t{]}}
@w{ @t{[}{&key} @{@i{var} | @r{(}@{@i{var} |
@r{(}@i{keyword-name} @i{var}@r{)}@}{)}@}{*} pt @r{[}@t{&allow-other-keys}@r{]}@t{]}@r{)}}
@w{ }
A @i{generic function lambda list} can contain the @i{lambda list keywords} shown
in Figure 3--14.
@group
@noindent
@w{ @b{&allow-other-keys} @b{&optional} }
@w{ @b{&key} @b{&rest} }
@noindent
@w{ Figure 3--14: Lambda List Keywords used by Generic Function Lambda Lists}
@end group
A @i{generic function lambda list} differs from an @i{ordinary lambda list}
in the following ways:
@table @asis
@item Required arguments
Zero or more @i{required parameters} must be specified.
@item Optional and keyword arguments
@i{Optional parameters} and @i{keyword parameters} may not have
default initial value forms nor use supplied-p parameters.
@item Use of @b{&aux}
The use of @b{&aux} is not allowed.
@end table
@node Specialized Lambda Lists, Macro Lambda Lists, Generic Function Lambda Lists, Lambda Lists
@subsection Specialized Lambda Lists
A @i{specialized lambda list}
@IGindex{specialized lambda list}
is used to @i{specialize} a @i{method}
for a particular @i{signature} and to describe how @i{arguments} matching
that @i{signature} are received by the @i{method}.
The @i{defined names} in Figure 3--15 use @i{specialized lambda lists}
in some way; see the dictionary entry for each for information about how.
@group
@noindent
@w{ defmethod defgeneric }
@noindent
@w{ Figure 3--15: Standardized Operators that use Specialized Lambda Lists}
@end group
A @i{specialized lambda list} can contain the @i{lambda list keywords} shown
in Figure 3--16.
@group
@noindent
@w{ @b{&allow-other-keys} @b{&key} @b{&rest} }
@w{ @b{&aux} @b{&optional} }
@noindent
@w{ Figure 3--16: Lambda List Keywords used by Specialized Lambda Lists}
@end group
A @i{specialized lambda list} is syntactically the same as an @i{ordinary lambda list}
except that each @i{required parameter} may optionally be associated with a @i{class}
or @i{object} for which that @i{parameter} is @i{specialized}.
@w{@i{lambda-list} ::=@r{(}@{@i{var} | @r{(}@i{var} @r{[}@i{specializer}@r{]}@r{)}@}{*}}
@w{ @t{[}{&optional} @{@i{var} |
@r{(}@i{var} @r{[}init-form @r{[}supplied-p-parameter@r{]}@r{]}@r{)}@}{*}@t{]}}
@w{ @t{[}{&rest} @i{var}@t{]}}
@w{ @t{[}{&key} @{@i{var} |
@r{(}@{@i{var} |
@r{(}@i{keyword-name} @i{var}@r{)}@}
@r{[}init-form @r{[}supplied-p-parameter@r{]}@r{]}@r{)}@}{*} @r{[}@t{&allow-other-keys}@r{]}@t{]}}
@w{ @t{[}{&aux} @{@i{var} | @r{(}@i{var} @r{[}@i{init-form}@r{]}@r{)}@}{*}@t{]}@r{)}}
@w{ }
@node Macro Lambda Lists, Destructuring Lambda Lists, Specialized Lambda Lists, Lambda Lists
@subsection Macro Lambda Lists
A @i{macro lambda list}
@IGindex{macro lambda list}
is used in describing @i{macros}
defined by the @i{operators} in Figure 3--17.
@group
@noindent
@w{ define-compiler-macro defmacro macrolet }
@w{ define-setf-expander }
@noindent
@w{ Figure 3--17: Operators that use Macro Lambda Lists}
@end group
With the additional restriction that
an @i{environment parameter} may appear only once
(at any of the positions indicated),
a @i{macro lambda list} has the following syntax:
{
@w{@i{reqvars} ::=@{@i{var} | !@i{pattern}@}{*}}
@w{@i{optvars} ::=@t{[}{&optional} @{@i{var} |
@r{(}{@{@i{var} | !@i{pattern}@}} @r{[}init-form @r{[}supplied-p-parameter@r{]}@r{]}@r{)}@}{*}@t{]}}
@w{@i{restvar} ::=@t{[}@{{@t{&rest}} | {&body}@} @i{@{@i{var} | !@i{pattern}@}}@t{]}}
@w{@i{keyvars} ::=@r{[}{&key} @{@i{var} |
@r{(}@{@i{var} |
@r{(}@i{keyword-name} {@{@i{var} | !@i{pattern}@}}@r{)}@}
@r{[}init-form @r{[}supplied-p-parameter@r{]}@r{]}@r{)}@}{*}}
@w{ @r{[}@t{&allow-other-keys}@r{]}@r{]}}
{
@w{@i{auxvars} ::=@t{[}{&aux} @{@i{var} | @r{(}{@i{var}} @r{[}@i{init-form}@r{]}@r{)}@}{*}@t{]}}
}
@w{@i{envvar} ::=@t{[}{&environment} @i{var}@t{]}}
@w{@i{wholevar} ::=@t{[}{&whole} @i{var}@t{]}}
@w{@i{lambda-list} ::=@r{(}!@i{wholevar} !@i{envvar} !@i{reqvars} !@i{envvar} !@i{optvars} !@i{envvar}}
@w{ !@i{restvar} !@i{envvar} !@i{keyvars} !@i{envvar} !@i{auxvars} !@i{envvar}@r{)} |}
@w{ @r{(}!@i{wholevar} !@i{envvar} !@i{reqvars} !@i{envvar} !@i{optvars} !@i{envvar} @t{.} @i{var}@r{)}}
@w{@i{pattern} ::=@r{(}!@i{wholevar} !@i{reqvars} !@i{optvars} !@i{restvar} !@i{keyvars} !@i{auxvars}@r{)} |}
@w{ @r{(}!@i{wholevar} !@i{reqvars} !@i{optvars} @t{.} @i{var}@r{)}}
}
A @i{macro lambda list} can contain
the @i{lambda list keywords} shown in Figure 3--18.
@group
@noindent
@w{ @b{&allow-other-keys} @b{&environment} @b{&rest} }
@w{ @b{&aux} @b{&key} @b{&whole} }
@w{ @b{&body} @b{&optional} }
@noindent
@w{ Figure 3--18: Lambda List Keywords used by Macro Lambda Lists}
@end group
@i{Optional parameters} (introduced by @b{&optional}) and
@i{keyword parameters} (introduced by @b{&key})
can be supplied in a @i{macro lambda list},
just as in an @i{ordinary lambda list}.
Both may contain default initialization forms and @i{supplied-p parameters}.
@b{&body}
@IRindex{&body}
is identical in function to @b{&rest},
but it can be used to inform certain output-formatting
and editing functions that the remainder of the @i{form} is
treated as a body, and should be indented accordingly.
Only one of @b{&body} or @b{&rest} can be used at any particular level;
see @ref{Destructuring by Lambda Lists}.
@b{&body} can appear at any level of a
@i{macro lambda list};
for details, see @ref{Destructuring by Lambda Lists}.
@b{&whole}
@IRindex{&whole}
is followed by a single variable that is bound to the
entire macro-call form; this is the value that the @i{macro function}
receives as its first argument.
If @b{&whole} and a following variable appear,
they must appear first in @i{lambda-list},
before any other parameter or @i{lambda list keyword}.
@b{&whole} can appear at any level of a @i{macro lambda list}.
At inner levels, the @b{&whole} variable is bound to
the corresponding part of the argument,
as with @b{&rest}, but unlike @b{&rest}, other arguments are also allowed.
The use of @b{&whole} does not affect the pattern of arguments
specified.
@b{&environment}
@IRindex{&environment}
is followed by a single variable that is bound
to an @i{environment} representing the @i{lexical environment} in which the
macro call is to be interpreted.
This @i{environment}
should be used with
@b{macro-function},
@b{get-setf-expansion},
@b{compiler-macro-function},
and
@b{macroexpand}
(for example) in computing the expansion of the macro, to ensure that any
@i{lexical bindings} or definitions established in the
@i{compilation environment} are taken into account.
@b{&environment} can only appear at the top level of a
@i{macro lambda list}, and can only
appear once, but can appear anywhere in that list;
the @b{&environment} @i{parameter} is @i{bound} along with @b{&whole}
before any other @i{variables} in the @i{lambda list}, regardless of where
@b{&environment} appears in the @i{lambda list}.
The @i{object} that is bound to the
@i{environment parameter} has @i{dynamic extent}.
Destructuring allows a @i{macro lambda list} to express
the structure of a macro call syntax.
If no @i{lambda list keywords} appear,
then the @i{macro lambda list} is a @i{tree}
containing parameter names at the leaves.
The pattern and the @i{macro form} must have compatible @i{tree structure};
that is, their @i{tree structure} must be equivalent,
or it must differ only in that some @i{leaves} of the pattern
match @i{non-atomic} @i{objects} of the @i{macro form}.
For information about error detection in this @i{situation},
see @ref{Destructuring Mismatch}.
A destructuring @i{lambda list}
(whether at top level or embedded)
can
be dotted, ending
in a parameter name. This situation is treated exactly as if the
parameter name that ends the @i{list} had appeared preceded by @b{&rest}.
It is permissible for a @i{macro} @i{form} (or a @i{subexpression} of a
@i{macro} @i{form})
to be a @i{dotted list}
only when @t{(... &rest var)} or @t{(... . var)} is used to match
it. It is the responsibility of the @i{macro} to recognize and deal
with such situations.
[Editorial Note by KMP: Apparently the dotted-macro-forms cleanup doesn't allow for
the macro to `manually' notice dotted forms and fix them as well.
It shouldn't be required that this be done only by &REST or
a dotted pattern; it should only matter that ultimately the
non-macro result of a full-macro expansion not contain dots.
Anyway, I plan to address this editorially unless someone
raises an objection.]
@menu
* Destructuring by Lambda Lists::
* Data-directed Destructuring by Lambda Lists::
* Examples of Data-directed Destructuring by Lambda Lists::
* Lambda-list-directed Destructuring by Lambda Lists::
@end menu
@node Destructuring by Lambda Lists, Data-directed Destructuring by Lambda Lists, Macro Lambda Lists, Macro Lambda Lists
@subsubsection Destructuring by Lambda Lists
Anywhere in a @i{macro lambda list} where a parameter
name can appear, and where @i{ordinary lambda list} syntax
(as described in @ref{Ordinary Lambda Lists}) does not
otherwise allow a @i{list}, a @i{destructuring lambda list}
can appear in place
of the parameter name. When this is done, then the argument
that would match the parameter is treated as a (possibly dotted) @i{list},
to be used as an argument list for satisfying the
parameters in the embedded @i{lambda list}.
This is known as destructuring.
Destructuring is the process of decomposing a compound @i{object} into
its component parts, using an abbreviated, declarative syntax, rather
than writing it out by hand using the primitive component-accessing
functions. Each component part is bound to a variable.
A destructuring operation requires an @i{object} to be decomposed,
a pattern that specifies what components are to be extracted, and the names
of the variables whose values are to be the components.
@node Data-directed Destructuring by Lambda Lists, Examples of Data-directed Destructuring by Lambda Lists, Destructuring by Lambda Lists, Macro Lambda Lists
@subsubsection Data-directed Destructuring by Lambda Lists
In data-directed destructuring,
the pattern is a sample @i{object} of the @i{type} to be decomposed.
Wherever a component is to be extracted,
a @i{symbol} appears in the pattern;
this @i{symbol} is the name of the variable whose value will be that component.
@node Examples of Data-directed Destructuring by Lambda Lists, Lambda-list-directed Destructuring by Lambda Lists, Data-directed Destructuring by Lambda Lists, Macro Lambda Lists
@subsubsection Examples of Data-directed Destructuring by Lambda Lists
An example pattern is
@t{(a b c)}
which destructures a list of three elements. The variable @t{a} is assigned
to the first element, @t{b} to the second, etc. A more complex example
is
@t{((first . rest) . more)}
The important features of data-directed destructuring are its syntactic
simplicity and the ability to extend it to lambda-list-directed destructuring.
@node Lambda-list-directed Destructuring by Lambda Lists, , Examples of Data-directed Destructuring by Lambda Lists, Macro Lambda Lists
@subsubsection Lambda-list-directed Destructuring by Lambda Lists
An extension of data-directed destructuring of @i{trees} is
lambda-list-directed destructuring. This derives from the analogy
between the three-element destructuring pattern
@t{(first second third)}
and the three-argument @i{lambda list}
@t{(first second third)}
Lambda-list-directed destructuring is identical to data-directed destructuring
if no @i{lambda list keywords} appear in the pattern.
Any list in the pattern (whether a sub-list or the whole pattern itself)
that contains a @i{lambda list keyword} is interpreted specially.
Elements of the list to the left of the first
@i{lambda list keyword} are treated as destructuring patterns, as usual, but the
remaining elements of the list are treated like a function's
@i{lambda list}
except that where a variable would normally be required, an arbitrary
destructuring pattern is allowed. Note that in case of ambiguity,
@i{lambda list} syntax is preferred over destructuring syntax. Thus, after
@b{&optional} a list of elements is a list of a destructuring pattern
and a default value form.
The detailed behavior of each @i{lambda list keyword} in a
lambda-list-directed destructuring
pattern is as follows:
@table @asis
@item @b{&optional}
Each following element is a variable or a list of a destructuring
pattern, a default value form, and a supplied-p variable. The default value and
the supplied-p variable can be omitted.
If the list being destructured ends
early, so that it does not have an element to match against this destructuring
(sub)-pattern, the default form is evaluated and destructured instead. The
supplied-p variable receives the value
@b{nil} if the default form is used, @b{t} otherwise.
@item @b{&rest}, @b{&body}
The next element is a destructuring pattern that matches the
rest of the list. @b{&body} is identical to @b{&rest} but declares that what
is being matched is a list of forms that constitutes the body of @i{form}.
This next element must be the last unless a @i{lambda list keyword} follows it.
@item @b{&aux}
The remaining elements are not destructuring patterns at all, but are
auxiliary variable bindings.
@item @b{&whole}
The next element is a destructuring pattern that matches the entire
form in a macro, or the entire @i{subexpression} at inner levels.
@item @b{&key}
Each following element is one of
@table @asis
@item @t{}
a @i{variable},
@item or
a list of a variable,
an optional initialization form,
and an optional supplied-p variable.
@item or
a list of a list of a keyword and a destructuring pattern,
an optional initialization form,
and an optional supplied-p variable.
@end table
The rest of the list being destructured
is taken to be alternating keywords and values and is taken apart appropriately.
@item @b{&allow-other-keys}
Stands by itself.
@end table
@node Destructuring Lambda Lists, Boa Lambda Lists, Macro Lambda Lists, Lambda Lists
@subsection Destructuring Lambda Lists
A @i{destructuring lambda list}
@IGindex{destructuring lambda list}
is used by @b{destructuring-bind}.
@i{Destructuring lambda lists} are closely related to
@i{macro lambda lists}; see @ref{Macro Lambda Lists}.
A @i{destructuring lambda list} can contain all of the
@i{lambda list keywords} listed for @i{macro lambda lists}
except for @b{&environment}, and supports destructuring in the
same way. Inner @i{lambda lists} nested within a @i{macro lambda list}
have the syntax of @i{destructuring lambda lists}.
A @i{destructuring lambda list} has the following syntax:
{
@w{@i{reqvars} ::=@{@i{var} | !@i{lambda-list}@}{*}}
@w{@i{optvars} ::=@t{[}{&optional} @{@i{var} |
@r{(}{@{@i{var} | !@i{lambda-list}@}} @r{[}init-form @r{[}supplied-p-parameter@r{]}@r{]}@r{)}@}{*}@t{]}}
@w{@i{restvar} ::=@t{[}@{{@t{&rest}} | {&body}@} @i{@{@i{var} | !@i{lambda-list}@}}@t{]}}
@w{@i{keyvars} ::=@r{[}{&key} @{@i{var} |
@r{(}@{@i{var} |
@r{(}@i{keyword-name} {@{@i{var} | !@i{lambda-list}@}}@r{)}@}
@r{[}init-form @r{[}supplied-p-parameter@r{]}@r{]}@r{)}@}{*}}
@w{ @r{[}@t{&allow-other-keys}@r{]}@r{]}}
{
@w{@i{auxvars} ::=@t{[}{&aux} @{@i{var} | @r{(}{@i{var}} @r{[}@i{init-form}@r{]}@r{)}@}{*}@t{]}}
}
@w{@i{envvar} ::=@t{[}{&environment} @i{var}@t{]}}
@w{@i{wholevar} ::=@t{[}{&whole} @i{var}@t{]}}
@w{@i{lambda-list} ::=@r{(}!@i{wholevar} !@i{reqvars} !@i{optvars} !@i{restvar} !@i{keyvars} !@i{auxvars}@r{)} |}
@w{ @r{(}!@i{wholevar} !@i{reqvars} !@i{optvars} @t{.} @i{var}@r{)}}
}
@node Boa Lambda Lists, Defsetf Lambda Lists, Destructuring Lambda Lists, Lambda Lists
@subsection Boa Lambda Lists
A @i{boa lambda list}
@IGindex{boa lambda list}
is a @i{lambda list} that is syntactically
like an @i{ordinary lambda list}, but that is processed in
``@b{b}y @b{o}rder of @b{a}rgument'' style.
A @i{boa lambda list} is used only in a @b{defstruct} @i{form},
when explicitly specifying the @i{lambda list}
of a constructor @i{function} (sometimes called a ``boa constructor'').
The @b{&optional}, @b{&rest}, @b{&aux},
@b{&key}, and @b{&allow-other-keys}
@i{lambda list keywords} are recognized in a @i{boa lambda list}.
The way these @i{lambda list keywords} differ from their
use in an @i{ordinary lambda list} follows.
Consider this example, which describes how @b{destruct} processes
its @t{:constructor} option.
@example
(:constructor create-foo
(a &optional b (c 'sea) &rest d &aux e (f 'eff)))
@end example
This defines @t{create-foo} to be a constructor of one or more arguments.
The first argument is used to initialize the @t{a} slot. The second
argument is used to initialize the @t{b} slot. If there isn't any
second argument, then the default value given in the body of the
@b{defstruct} (if given) is used instead.
The third argument is used to
initialize the @t{c} slot. If there isn't any third argument, then the
symbol @t{sea} is used instead. Any arguments following the third
argument are collected into a @i{list}
and used to initialize the @t{d}
slot. If there are three or fewer arguments, then @b{nil} is placed in
the @t{d} slot. The @t{e} slot is not initialized;
its initial value is @i{implementation-defined}.
Finally, the @t{f} slot is initialized to contain the symbol @t{eff}.
@b{&key} and @b{&allow-other-keys} arguments default
in a manner similar to that of @b{&optional} arguments: if no default
is supplied in the @i{lambda list} then the default value
given in the body of the @b{defstruct} (if given) is used instead.
For example:
@example
(defstruct (foo (:constructor CREATE-FOO (a &optional b (c 'sea)
&key (d 2)
&aux e (f 'eff))))
(a 1) (b 2) (c 3) (d 4) (e 5) (f 6))
(create-foo 10) @result{} #S(FOO A 10 B 2 C SEA D 2 E @i{implemention-dependent} F EFF)
(create-foo 10 'bee 'see :d 'dee)
@result{} #S(FOO A 10 B BEE C SEE D DEE E @i{implemention-dependent} F EFF)
@end example
If keyword arguments of the form
@t{((@i{key} @i{var}) @r{[}@i{default} @r{[}@i{svar}@r{]}@r{]})}
are specified, the @i{slot} @i{name} is matched with @i{var}
(not @i{key}).
The actions taken in the @t{b} and @t{e} cases were carefully
chosen to allow the user to specify all possible behaviors.
The @b{&aux} variables can be used to completely override the default
initializations given in the body.
If no default value is supplied for an @i{aux variable} variable,
the consequences are undefined if an attempt is later made to read
the corresponding @i{slot}'s value before a value is explicitly assigned.
If such a @i{slot} has a @t{:type} option specified,
this suppressed initialization does not imply a type mismatch situation;
the declared type is only required to apply when the @i{slot} is finally assigned.
With this definition, the following can be written:
@example
(create-foo 1 2)
@end example
instead of
@example
(make-foo :a 1 :b 2)
@end example
and @t{create-foo} provides defaulting different
from that of @t{make-foo}.
Additional arguments that do not correspond to slot names but
are merely present to supply values used in subsequent initialization
computations are allowed.
For example, in the definition
@example
(defstruct (frob (:constructor create-frob
(a &key (b 3 have-b) (c-token 'c)
(c (list c-token (if have-b 7 2))))))
a b c)
@end example
the @t{c-token} argument is used merely to supply a value used in the
initialization of the @t{c} slot. The @i{supplied-p parameters}
associated with @i{optional parameters} and @i{keyword parameters}
might also be used this way.
@node Defsetf Lambda Lists, Deftype Lambda Lists, Boa Lambda Lists, Lambda Lists
@subsection Defsetf Lambda Lists
A @i{defsetf lambda list}
@IGindex{defsetf lambda list}
is used by @b{defsetf}.
A @i{defsetf lambda list} has the following syntax:
@w{@i{lambda-list} ::=@r{(}@{@i{var}@}{*}}
@w{ @t{[}{&optional} @{@i{var} |
@r{(}@i{var} @r{[}init-form @r{[}supplied-p-parameter@r{]}@r{]}@r{)}@}{*}@t{]}}
@w{ @t{[}{&rest} @i{var}@t{]}}
@w{ @t{[}{&key} @{@i{var} |
@r{(}@{@i{var} |
@r{(}@i{keyword-name} @i{var}@r{)}@}
@r{[}init-form @r{[}supplied-p-parameter@r{]}@r{]}@r{)}@}{*} pt @r{[}@t{&allow-other-keys}@r{]}@t{]}}
@w{ @t{[}{&environment} @i{var}@t{]}}
A @i{defsetf lambda list} can contain the @i{lambda list keywords} shown
in Figure 3--19.
@group
@noindent
@w{ @b{&allow-other-keys} @b{&key} @b{&rest} }
@w{ @b{&environment} @b{&optional} }
@noindent
@w{ Figure 3--19: Lambda List Keywords used by Defsetf Lambda Lists}
@end group
A @i{defsetf lambda list} differs from an @i{ordinary lambda list}
only in that it does not permit the use of @b{&aux},
and that it permits use of @b{&environment},
which introduces an @i{environment parameter}.
@node Deftype Lambda Lists, Define-modify-macro Lambda Lists, Defsetf Lambda Lists, Lambda Lists
@subsection Deftype Lambda Lists
A @i{deftype lambda list}
@IGindex{deftype lambda list}
is used by @b{deftype}.
A @i{deftype lambda list} has the same syntax as a @i{macro lambda list},
and can therefore contain the @i{lambda list keywords} as a @i{macro lambda list}.
A @i{deftype lambda list} differs from a @i{macro lambda list}
only in that if no @i{init-form} is supplied for an @i{optional parameter}
or @i{keyword parameter} in the @i{lambda-list}, the default @i{value}
for that @i{parameter} is the @i{symbol} @b{*} (rather than @b{nil}).
@node Define-modify-macro Lambda Lists, Define-method-combination Arguments Lambda Lists, Deftype Lambda Lists, Lambda Lists
@subsection Define-modify-macro Lambda Lists
A @i{define-modify-macro lambda list}
@IGindex{define-modify-macro lambda list}
is used by
@b{define-modify-macro}.
A @i{define-modify-macro lambda list} can contain the
@i{lambda list keywords} shown in Figure 3--20.
@group
@noindent
@w{ @b{&optional} @b{&rest} }
@noindent
@w{ Figure 3--20: Lambda List Keywords used by Define-modify-macro Lambda Lists}
@end group
@i{Define-modify-macro lambda lists} are similar to
@i{ordinary lambda lists}, but do not support keyword arguments.
@b{define-modify-macro} has no need match keyword arguments, and
a @i{rest parameter} is sufficient. @i{Aux variables} are also
not supported, since @b{define-modify-macro} has no body @i{forms}
which could refer to such @i{bindings}. See the @i{macro} @b{define-modify-macro}.
@node Define-method-combination Arguments Lambda Lists, Syntactic Interaction of Documentation Strings and Declarations, Define-modify-macro Lambda Lists, Lambda Lists
@subsection Define-method-combination Arguments Lambda Lists
A @i{define-method-combination arguments lambda list}
@IGindex{define-method-combination arguments lambda list}
is used by
the @t{:arguments} option to @b{define-method-combination}.
A @i{define-method-combination arguments lambda list} can contain the
@i{lambda list keywords} shown in Figure 3--21.
@group
@noindent
@w{ @b{&allow-other-keys} @b{&key} @b{&rest} }
@w{ @b{&aux} @b{&optional} @b{&whole} }
@noindent
@w{ Figure 3--21: Lambda List Keywords used by Define-method-combination arguments Lambda Lists}
@end group
@i{Define-method-combination arguments lambda lists} are similar to
@i{ordinary lambda lists}, but also permit the use of @b{&whole}.
@node Syntactic Interaction of Documentation Strings and Declarations, , Define-method-combination Arguments Lambda Lists, Lambda Lists
@subsection Syntactic Interaction of Documentation Strings and Declarations
In a number of situations, a @i{documentation string} can appear amidst a
series of @b{declare} @i{expressions} prior to a series of @i{forms}.
In that case, if a @i{string} S appears where a @i{documentation string} is
permissible and is not followed by
either a @b{declare} @i{expression}
or a @i{form}
then S is taken to be a @i{form};
otherwise, S is taken as a @i{documentation string}.
The consequences are unspecified if more than one such @i{documentation string}
is present.
@c end of including concept-bvl
@node Error Checking in Function Calls, Traversal Rules and Side Effects, Lambda Lists, Evaluation and Compilation
@section Error Checking in Function Calls
@c including concept-args
@menu
* Argument Mismatch Detection::
@end menu
@node Argument Mismatch Detection, , Error Checking in Function Calls, Error Checking in Function Calls
@subsection Argument Mismatch Detection
@menu
* Safe and Unsafe Calls::
* Error Detection Time in Safe Calls::
* Too Few Arguments::
* Too Many Arguments::
* Unrecognized Keyword Arguments::
* Invalid Keyword Arguments::
* Odd Number of Keyword Arguments::
* Destructuring Mismatch::
* Errors When Calling a Next Method::
@end menu
@node Safe and Unsafe Calls, Error Detection Time in Safe Calls, Argument Mismatch Detection, Argument Mismatch Detection
@subsubsection Safe and Unsafe Calls
A @i{call} is a @i{safe call}
@IGindex{safe call}
if each of the following is
either @i{safe} @i{code} or @i{system code} (other than
@i{system code} that results from @i{macro expansion} of
@i{programmer code}):
@table @asis
@item @t{*}
the @i{call}.
@item @t{*}
the definition of the @i{function} being @i{called}.
@item @t{*}
the point of @i{functional evaluation}
@end table
The following special cases require some elaboration:
@table @asis
@item @t{*}
If the @i{function} being called is a @i{generic function},
it is considered @i{safe} if all of the following are
@i{safe code} or @i{system code}:
@table @asis
@item --
its definition (if it was defined explicitly).
@item --
the @i{method} definitions for all @i{applicable} @i{methods}.
@item --
the definition of its @i{method combination}.
@end table
@item @t{*}
For the form @t{(coerce @i{x} 'function)},
where @i{x} is a @i{lambda expression},
the value of the @i{optimize quality} @b{safety}
in the global environment at the time the @b{coerce}
is @i{executed} applies to the resulting @i{function}.
@item @t{*}
For a call to the @i{function} @b{ensure-generic-function}, the value of the
@i{optimize quality} @b{safety} in the @i{environment}
@i{object} passed as the @t{:environment} @i{argument} applies
to the resulting @i{generic function}.
@item @t{*}
For a call to @b{compile} with a @i{lambda expression} as the
@i{argument}, the value of the @i{optimize quality} @b{safety}
in the @i{global environment} at the time @b{compile} is @i{called}
applies to the resulting @i{compiled function}.
@item @t{*}
For a call to @b{compile} with only one argument, if the original definition
of the @i{function} was @i{safe}, then the resulting @i{compiled function}
must also be @i{safe}.
@item @t{*}
A @i{call} to a @i{method} by @b{call-next-method} must be
considered @i{safe} if each of the following is
@i{safe code} or @i{system code}:
@table @asis
@item --
the definition of the @i{generic function} (if it was defined explicitly).
@item --
the @i{method} definitions for all @i{applicable} @i{methods}.
@item --
the definition of the @i{method combination}.
@item --
the point of entry into the body of the @i{method defining form},
where the @i{binding} of @b{call-next-method} is established.
@item --
the point of @i{functional evaluation} of the name @b{call-next-method}.
@end table
@end table
An @i{unsafe call}
@IGindex{unsafe call}
is a @i{call} that is not a @i{safe call}.
The informal intent is that the @i{programmer} can rely on a @i{call}
to be @i{safe}, even when @i{system code} is involved, if all reasonable
steps have been taken to ensure that the @i{call} is @i{safe}.
For example, if a @i{programmer} calls @b{mapcar} from @i{safe}
@i{code} and supplies a @i{function} that was @i{compiled}
as @i{safe}, the @i{implementation} is required to ensure that
@b{mapcar} makes a @i{safe call} as well.
@node Error Detection Time in Safe Calls, Too Few Arguments, Safe and Unsafe Calls, Argument Mismatch Detection
@subsubsection Error Detection Time in Safe Calls
If an error is signaled in a @i{safe call},
the exact point of the @i{signal} is @i{implementation-dependent}.
In particular, it might be signaled at compile time or at run time,
and if signaled at run time,
it might be prior to, during, or after @i{executing} the @i{call}.
However, it is always prior to the execution of the body of the @i{function}
being @i{called}.
@node Too Few Arguments, Too Many Arguments, Error Detection Time in Safe Calls, Argument Mismatch Detection
@subsubsection Too Few Arguments
It is not permitted to supply too few @i{arguments} to a @i{function}.
Too few arguments means fewer @i{arguments} than the number of @i{required parameters}
for the @i{function}.
If this @i{situation} occurs in a @i{safe call},
an error of @i{type} @b{program-error} must be signaled;
and in an @i{unsafe call} the @i{situation} has undefined consequences.
@node Too Many Arguments, Unrecognized Keyword Arguments, Too Few Arguments, Argument Mismatch Detection
@subsubsection Too Many Arguments
It is not permitted to supply too many @i{arguments} to a @i{function}.
Too many arguments means more @i{arguments} than the number of @i{required parameters}
plus the number of @i{optional parameters}; however, if the @i{function}
uses @b{&rest} or @b{&key}, it is not possible for it to receive too many arguments.
If this @i{situation} occurs in a @i{safe call},
an error of @i{type} @b{program-error} must be signaled;
and in an @i{unsafe call} the @i{situation} has undefined consequences.
@node Unrecognized Keyword Arguments, Invalid Keyword Arguments, Too Many Arguments, Argument Mismatch Detection
@subsubsection Unrecognized Keyword Arguments
It is not permitted to supply a keyword argument to a @i{function}
using a name that is not recognized by that @i{function}
unless keyword argument checking is suppressed as described
in @ref{Suppressing Keyword Argument Checking}.
If this @i{situation} occurs in a @i{safe call},
an error of @i{type} @b{program-error} must be signaled;
and in an @i{unsafe call} the @i{situation} has undefined consequences.
@node Invalid Keyword Arguments, Odd Number of Keyword Arguments, Unrecognized Keyword Arguments, Argument Mismatch Detection
@subsubsection Invalid Keyword Arguments
It is not permitted to supply a keyword argument to a @i{function}
using a name that is not a @i{symbol}.
If this @i{situation} occurs in a @i{safe call},
an error of @i{type} @b{program-error} must be signaled
unless keyword argument checking is suppressed as described
in @ref{Suppressing Keyword Argument Checking};
and in an @i{unsafe call} the @i{situation} has undefined consequences.
@node Odd Number of Keyword Arguments, Destructuring Mismatch, Invalid Keyword Arguments, Argument Mismatch Detection
@subsubsection Odd Number of Keyword Arguments
An odd number of @i{arguments} must not be supplied for the @i{keyword parameters}.
If this @i{situation} occurs in a @i{safe call},
an error of @i{type} @b{program-error} must be signaled
unless keyword argument checking is suppressed as described
in @ref{Suppressing Keyword Argument Checking};
and in an @i{unsafe call} the @i{situation} has undefined consequences.
@node Destructuring Mismatch, Errors When Calling a Next Method, Odd Number of Keyword Arguments, Argument Mismatch Detection
@subsubsection Destructuring Mismatch
When matching a @i{destructuring lambda list} against a @i{form},
the pattern and the @i{form} must have compatible @i{tree structure},
as described in @ref{Macro Lambda Lists}.
Otherwise, in a @i{safe call},
an error of @i{type} @b{program-error} must be signaled;
and in an @i{unsafe call} the @i{situation} has undefined consequences.
@node Errors When Calling a Next Method, , Destructuring Mismatch, Argument Mismatch Detection
@subsubsection Errors When Calling a Next Method
If @b{call-next-method} is called with @i{arguments}, the ordered
set of @i{applicable} @i{methods} for the changed set of @i{arguments}
for @b{call-next-method} must be the same as the ordered set of
@i{applicable} @i{methods} for the original @i{arguments} to the
@i{generic function}, or else an error should be signaled.
The comparison between the set of methods applicable to the
new arguments and the set applicable to the original arguments is
insensitive to order differences among methods with the same
specializers.
If @b{call-next-method} is called with @i{arguments} that specify
a different ordered set of @i{applicable} methods and there is no
@i{next method} available, the test for different methods and the
associated error signaling (when present) takes precedence over calling
@b{no-next-method}.
@c end of including concept-args
@node Traversal Rules and Side Effects, Destructive Operations, Error Checking in Function Calls, Evaluation and Compilation
@section Traversal Rules and Side Effects
@c including concept-traversal
The consequences are undefined
when @i{code} executed during an @i{object-traversing} operation
destructively modifies the @i{object} in a way that might affect the
ongoing traversal operation.
In particular, the following rules apply.
@table @asis
@item @b{List traversal}
For @i{list} traversal operations, the @i{cdr} chain of the
@i{list} is not allowed to be destructively modified.
@item @b{Array traversal}
For @i{array} traversal operations, the @i{array} is not allowed
to be adjusted and its @i{fill pointer}, if any, is not allowed to
be changed.
@item @b{Hash-table traversal}
For @i{hash table} traversal operations, new elements may not be added
or deleted except that the element corresponding to the current hash key
may be changed or removed.
@item @b{Package traversal}
For @i{package} traversal operations (@i{e.g.}, @b{do-symbols}),
new @i{symbols} may not be @i{interned} in or @i{uninterned}
from the @i{package} being traversed
or any @i{package} that it uses except that the
current @i{symbol} may be @i{uninterned} from the @i{package}
being traversed.
@end table
@c end of including concept-traversal
@node Destructive Operations, Evaluation and Compilation Dictionary, Traversal Rules and Side Effects, Evaluation and Compilation
@section Destructive Operations
@c including concept-destruction
@menu
* Modification of Literal Objects::
* Transfer of Control during a Destructive Operation::
@end menu
@node Modification of Literal Objects, Transfer of Control during a Destructive Operation, Destructive Operations, Destructive Operations
@subsection Modification of Literal Objects
The consequences are undefined if @i{literal} @i{objects}
are destructively modified. For this purpose, the following operations
are considered @i{destructive}:
@table @asis
@item @b{random-state}
Using it as an @i{argument} to the @i{function} @b{random}.
@item @b{cons}
Changing the @i{car}_1 or @i{cdr}_1 of the @i{cons},
or performing a @i{destructive} operation on an @i{object} which is either
the @i{car}_2 or the @i{cdr}_2 of the @i{cons}.
@item @b{array}
Storing a new value into some element of the @i{array},
or performing a @i{destructive} operation
on an @i{object} that is already such an @i{element}.
Changing the @i{fill pointer}, @i{dimensions}, or displacement of
the @i{array} (regardless of whether the @i{array} is @i{actually adjustable}).
Performing a @i{destructive} operation on another @i{array}
that is displaced to the @i{array} or that otherwise shares its contents
with the @i{array}.
@item @b{hash-table}
Performing a @i{destructive} operation on any @i{key}.
Storing a new @i{value}_4 for any @i{key},
or performing a @i{destructive} operation
on any @i{object} that is such a @i{value}.
Adding or removing entries from the @i{hash table}.
@item @b{structure-object}
Storing a new value into any slot,
or performing a @i{destructive} operation on an @i{object}
that is the value of some slot.
@item @b{standard-object}
Storing a new value into any slot,
or performing a @i{destructive} operation on an @i{object}
that is the value of some slot.
Changing the class of the @i{object} (@i{e.g.}, using the @i{function} @b{change-class}).
@item @b{readtable}
Altering the @i{readtable case}.
Altering the syntax type of any character in this readtable.
Altering the @i{reader macro function} associated with any @i{character}
in the @i{readtable}, or altering the @i{reader macro functions}
associated with @i{characters} defined as @i{dispatching macro characters}
in the @i{readtable}.
@item @b{stream}
Performing I/O operations on the @i{stream},
or @i{closing} the @i{stream}.
@item All other standardized types
[This category includes, for example, @b{character},
@b{condition},
@b{function},
@b{method-combination},
@b{method},
@b{number},
@b{package},
@b{pathname},
@b{restart},
and @b{symbol}.]
There are no @i{standardized} @i{destructive} operations
defined on @i{objects} of these @i{types}.
@end table
@node Transfer of Control during a Destructive Operation, , Modification of Literal Objects, Destructive Operations
@subsection Transfer of Control during a Destructive Operation
Should a transfer of control out of a @i{destructive} operation occur
(@i{e.g.}, due to an error) the state of the @i{object} being modified is
@i{implementation-dependent}.
@menu
* Examples of Transfer of Control during a Destructive Operation::
@end menu
@node Examples of Transfer of Control during a Destructive Operation, , Transfer of Control during a Destructive Operation, Transfer of Control during a Destructive Operation
@subsubsection Examples of Transfer of Control during a Destructive Operation
The following examples illustrate some of the many ways in which the
@i{implementation-dependent} nature of the modification can manifest
itself.
@example
(let ((a (list 2 1 4 3 7 6 'five)))
(ignore-errors (sort a #'<))
a)
@result{} (1 2 3 4 6 7 FIVE)
@i{OR}@result{} (2 1 4 3 7 6 FIVE)
@i{OR}@result{} (2)
(prog foo ((a (list 1 2 3 4 5 6 7 8 9 10)))
(sort a #'(lambda (x y) (if (zerop (random 5)) (return-from foo a) (> x y)))))
@result{} (1 2 3 4 5 6 7 8 9 10)
@i{OR}@result{} (3 4 5 6 2 7 8 9 10 1)
@i{OR}@result{} (1 2 4 3)
@end example
@c end of including concept-destruction
@node Evaluation and Compilation Dictionary, , Destructive Operations, Evaluation and Compilation
@section Evaluation and Compilation Dictionary
@c including dict-eval-compile
@menu
* lambda (Symbol)::
* lambda::
* compile::
* eval::
* eval-when::
* load-time-value::
* quote::
* compiler-macro-function::
* define-compiler-macro::
* defmacro::
* macro-function::
* macroexpand::
* define-symbol-macro::
* symbol-macrolet::
* *macroexpand-hook*::
* proclaim::
* declaim::
* declare::
* ignore::
* dynamic-extent::
* type::
* inline::
* ftype::
* declaration::
* optimize::
* special::
* locally::
* the::
* special-operator-p::
* constantp::
@end menu
@node lambda (Symbol), lambda, Evaluation and Compilation Dictionary, Evaluation and Compilation Dictionary
@subsection lambda [Symbol]
@subsubheading Syntax::
@code{lambda} @i{lambda-list {[[@{@i{declaration}@}{*} | @i{documentation}]]} @{@i{form}@}{*}}
@subsubheading Arguments::
@i{lambda-list}---an @i{ordinary lambda list}.
@i{declaration}---a @b{declare} @i{expression}; not evaluated.
@i{documentation}---a @i{string}; not evaluated.
@i{form}---a @i{form}.
@subsubheading Description::
A @i{lambda expression} is a @i{list} that can be used in place of a
@i{function name} in certain contexts to denote a @i{function} by
directly describing its behavior rather than indirectly by referring to the
name of an @i{established} @i{function}.
@i{Documentation} is attached to the denoted @i{function} (if any
is actually created) as a @i{documentation string}.
@subsubheading See Also::
@b{function},
@ref{documentation; (setf documentation)}
,
@ref{Lambda Expressions},
@ref{Lambda Forms},
@ref{Syntactic Interaction of Documentation Strings and Declarations}
@subsubheading Notes::
The @i{lambda form}
@example
((lambda @i{lambda-list} . @i{body}) . @i{arguments})
@end example
is semantically equivalent to the @i{function form}
@example
(funcall #'(lambda @i{lambda-list} . @i{body}) . @i{arguments})
@end example
@node lambda, compile, lambda (Symbol), Evaluation and Compilation Dictionary
@subsection lambda [Macro]
@code{lambda} @i{lambda-list {[[@{@i{declaration}@}{*} | @i{documentation}]]} @{@i{form}@}{*}} @result{} @i{@i{function}}
@subsubheading Arguments and Values::
@i{lambda-list}---an @i{ordinary lambda list}.
@i{declaration}---a @b{declare} @i{expression}; not evaluated.
@i{documentation}---a @i{string}; not evaluated.
@i{form}---a @i{form}.
@i{function}---a @i{function}.
@subsubheading Description::
Provides a shorthand notation for a @b{function} @i{special form}
involving a @i{lambda expression} such that:
@example
(lambda @i{lambda-list} {[[@{@i{declaration}@}{*} | @i{documentation}]]} @{@i{form}@}{*})
@equiv{} (function (lambda @i{lambda-list} {[[@{@i{declaration}@}{*} | @i{documentation}]]} @{@i{form}@}{*}))
@equiv{} #'(lambda @i{lambda-list} {[[@{@i{declaration}@}{*} | @i{documentation}]]} @{@i{form}@}{*})
@end example
@subsubheading Examples::
@example
(funcall (lambda (x) (+ x 3)) 4) @result{} 7
@end example
@subsubheading See Also::
@b{lambda} (symbol)
@subsubheading Notes::
This macro could be implemented by:
@example
(defmacro lambda (&whole form &rest bvl-decls-and-body)
(declare (ignore bvl-decls-and-body))
`#',form)
@end example
@node compile, eval, lambda, Evaluation and Compilation Dictionary
@subsection compile [Function]
@code{compile} @i{name {&optional} definition} @result{} @i{function, warnings-p, failure-p}
@subsubheading Arguments and Values::
@i{name}---a @i{function name}, or @b{nil}.
@i{definition}---a @i{lambda expression} or a @i{function}.
The default is the function definition of @i{name} if it names a @i{function},
or the @i{macro function} of @i{name} if it names a @i{macro}.
The consequences are undefined if no @i{definition} is supplied
when the @i{name} is @b{nil}.
@i{function}---the @i{function-name},
or a @i{compiled function}.
@i{warnings-p}---a @i{generalized boolean}.
@i{failure-p}---a @i{generalized boolean}.
@subsubheading Description::
Compiles an @i{interpreted function}.
@b{compile} produces a @i{compiled function} from @i{definition}.
If the @i{definition} is a @i{lambda expression},
it is coerced to a @i{function}.
If the @i{definition} is already a @i{compiled function},
@b{compile} either produces that function itself (@i{i.e.}, is an identity operation)
or an equivalent function.
[Editorial Note by KMP: There are a number of ambiguities here that still need resolution.]
If the @i{name} is @b{nil},
the resulting @i{compiled function} is returned directly as the @i{primary value}.
If a @i{non-nil} @i{name} is given,
then the resulting @i{compiled function} replaces
the existing @i{function} definition of @i{name}
and the @i{name} is returned as the @i{primary value};
if @i{name} is a @i{symbol} that names a @i{macro},
its @i{macro function} is updated
and the @i{name} is returned as the @i{primary value}.
@i{Literal objects} appearing in code processed by
the @b{compile} function are neither copied nor @i{coalesced}.
The code resulting from the execution of @b{compile}
references @i{objects} that are @b{eql} to the corresponding
@i{objects} in the source code.
@b{compile} is permitted, but not required, to @i{establish}
a @i{handler} for @i{conditions} of @i{type} @b{error}.
For example, the @i{handler} might issue a warning and
restart compilation from some @i{implementation-dependent} point
in order to let the compilation proceed without manual intervention.
The @i{secondary value}, @i{warnings-p}, is @i{false}
if no @i{conditions} of @i{type} @b{error} or @b{warning}
were detected by the compiler, and @i{true} otherwise.
The @i{tertiary value}, @i{failure-p}, is @i{false}
if no @i{conditions} of @i{type} @b{error} or @b{warning}
(other than @b{style-warning})
were detected by the compiler, and @i{true} otherwise.
@subsubheading Examples::
@example
(defun foo () "bar") @result{} FOO
(compiled-function-p #'foo) @result{} @i{implementation-dependent}
(compile 'foo) @result{} FOO
(compiled-function-p #'foo) @result{} @i{true}
(setf (symbol-function 'foo)
(compile nil '(lambda () "replaced"))) @result{} #<Compiled-Function>
(foo) @result{} "replaced"
@end example
@subsubheading Affected By::
@b{*error-output*},
@b{*macroexpand-hook*}.
The presence of macro definitions and proclamations.
@subsubheading Exceptional Situations::
The consequences are undefined if the @i{lexical environment} surrounding the
@i{function} to be compiled contains any @i{bindings} other than those for
@i{macros}, @i{symbol macros}, or @i{declarations}.
For information about errors detected during the compilation process,
see @ref{Exceptional Situations in the Compiler}.
@subsubheading See Also::
@ref{compile-file}
@node eval, eval-when, compile, Evaluation and Compilation Dictionary
@subsection eval [Function]
@code{eval} @i{form} @result{} @i{@{@i{result}@}{*}}
@subsubheading Arguments and Values::
@i{form}---a @i{form}.
@i{results}---the @i{values} @i{yielded} by the @i{evaluation} of @i{form}.
@subsubheading Description::
Evaluates @i{form} in the current @i{dynamic environment}
and the @i{null lexical environment}.
@b{eval} is a user interface to the evaluator.
The evaluator expands macro calls as if through the use of @b{macroexpand-1}.
Constants appearing in code
processed by @b{eval} are
not copied nor coalesced. The code resulting from the execution of
@b{eval}
references @i{objects}
that are @b{eql} to the corresponding @i{objects} in
the source code.
@subsubheading Examples::
@example
(setq form '(1+ a) a 999) @result{} 999
(eval form) @result{} 1000
(eval 'form) @result{} (1+ A)
(let ((a '(this would break if eval used local value))) (eval form))
@result{} 1000
@end example
@subsubheading See Also::
@b{macroexpand-1},
@ref{The Evaluation Model}
@subsubheading Notes::
To obtain the current dynamic value of a @i{symbol},
use of @b{symbol-value} is equivalent (and usually preferable)
to use of @b{eval}.
Note that an @b{eval} @i{form} involves two levels of @i{evaluation}
for its @i{argument}. First, @i{form} is @i{evaluated} by the
normal argument evaluation mechanism as would occur with any @i{call}.
The @i{object} that results from this normal @i{argument} @i{evaluation}
becomes the @i{value} of the @i{form} @i{parameter}, and is then
@i{evaluated} as part of the @b{eval} @i{form}.
For example:
@example
(eval (list 'cdr (car '((quote (a . b)) c)))) @result{} b
@end example
The @i{argument} @i{form} @t{(list 'cdr (car '((quote (a . b)) c)))} is evaluated
in the usual way to produce the @i{argument} @t{(cdr (quote (a . b)))};
@b{eval} then evaluates its @i{argument}, @t{(cdr (quote (a . b)))}, to produce @t{b}.
Since a single @i{evaluation} already occurs for any @i{argument} @i{form}
in any @i{function form},
@b{eval} is sometimes said to perform ``an extra level of evaluation.''
@node eval-when, load-time-value, eval, Evaluation and Compilation Dictionary
@subsection eval-when [Special Operator]
@code{eval-when} @i{@r{(}@{@i{situation}@}{*}@r{)} @{@i{form}@}{*}} @result{} @i{@{@i{result}@}{*}}
@subsubheading Arguments and Values::
@i{situation}---One of the @i{symbols}
@t{:compile-toplevel}
@IKindex{compile-toplevel}
,
@t{:load-toplevel}
@IKindex{load-toplevel}
,
@t{:execute}
@IKindex{execute}
,
@b{compile}
@IRindex{compile}
,
@b{load}
@IRindex{load}
, or
@b{eval}
@IRindex{eval}
.
The use of @b{eval}, @b{compile}, and @b{load} is deprecated.
@i{forms}---an @i{implicit progn}.
@i{results}---the @i{values} of the @i{forms} if they are executed,
or @b{nil} if they are not.
@subsubheading Description::
The body of an @b{eval-when} form is processed as an @i{implicit progn},
but only in the @i{situations} listed.
The use of the @i{situations} @t{:compile-toplevel} (or @t{compile}) and
@t{:load-toplevel} (or @t{load}) controls whether and when @i{evaluation}
occurs when @b{eval-when} appears as a @i{top level form} in
code processed by @b{compile-file}. See @ref{File Compilation}.
The use of the @i{situation} @t{:execute} (or @t{eval}) controls whether
evaluation occurs for other @b{eval-when} @i{forms}; that is,
those that are not @i{top level forms}, or those in code processed by
@b{eval} or @b{compile}. If the @t{:execute} situation is
specified in such a @i{form}, then the body @i{forms} are processed as
an @i{implicit progn}; otherwise, the @b{eval-when} @i{form}
returns @b{nil}.
@b{eval-when}
normally appears as a @i{top level form}, but it is meaningful
for it to appear as a @i{non-top-level form}.
However, the compile-time side
effects described in @ref{Compilation}
only take place when @b{eval-when} appears as a
@i{top level form}.
@subsubheading Examples::
One example of the use of @b{eval-when} is that for the
compiler to be able to read a file properly when it uses user-defined
@i{reader macros}, it is necessary to write
@example
(eval-when (:compile-toplevel :load-toplevel :execute)
(set-macro-character #\$ #'(lambda (stream char)
(declare (ignore char))
(list 'dollar (read stream))))) @result{} T
@end example
This causes the call to @b{set-macro-character} to be executed
in the compiler's execution environment, thereby modifying its
reader syntax table.
@example
;;; The EVAL-WHEN in this case is not at toplevel, so only the :EXECUTE
;;; keyword is considered. At compile time, this has no effect.
;;; At load time (if the LET is at toplevel), or at execution time
;;; (if the LET is embedded in some other form which does not execute
;;; until later) this sets (SYMBOL-FUNCTION 'FOO1) to a function which
;;; returns 1.
(let ((x 1))
(eval-when (:execute :load-toplevel :compile-toplevel)
(setf (symbol-function 'foo1) #'(lambda () x))))
;;; If this expression occurs at the toplevel of a file to be compiled,
;;; it has BOTH a compile time AND a load-time effect of setting
;;; (SYMBOL-FUNCTION 'FOO2) to a function which returns 2.
(eval-when (:execute :load-toplevel :compile-toplevel)
(let ((x 2))
(eval-when (:execute :load-toplevel :compile-toplevel)
(setf (symbol-function 'foo2) #'(lambda () x)))))
;;; If this expression occurs at the toplevel of a file to be compiled,
;;; it has BOTH a compile time AND a load-time effect of setting the
;;; function cell of FOO3 to a function which returns 3.
(eval-when (:execute :load-toplevel :compile-toplevel)
(setf (symbol-function 'foo3) #'(lambda () 3)))
;;; #4: This always does nothing. It simply returns NIL.
(eval-when (:compile-toplevel)
(eval-when (:compile-toplevel)
(print 'foo4)))
;;; If this form occurs at toplevel of a file to be compiled, FOO5 is
;;; printed at compile time. If this form occurs in a non-top-level
;;; position, nothing is printed at compile time. Regardless of context,
;;; nothing is ever printed at load time or execution time.
(eval-when (:compile-toplevel)
(eval-when (:execute)
(print 'foo5)))
;;; If this form occurs at toplevel of a file to be compiled, FOO6 is
;;; printed at compile time. If this form occurs in a non-top-level
;;; position, nothing is printed at compile time. Regardless of context,
;;; nothing is ever printed at load time or execution time.
(eval-when (:execute :load-toplevel)
(eval-when (:compile-toplevel)
(print 'foo6)))
@end example
@subsubheading See Also::
@ref{compile-file}
, @ref{Compilation}
@subsubheading Notes::
The following effects are logical consequences of the definition of
@b{eval-when}:
@table @asis
@item @t{*}
Execution of a single @b{eval-when}
expression executes the body code at most once.
@item @t{*}
@i{Macros} intended for use in @i{top level forms}
should be written so that side-effects are done by the @i{forms}
in the macro expansion. The macro-expander itself should not do
the side-effects.
For example:
Wrong:
@example
(defmacro foo ()
(really-foo)
`(really-foo))
@end example
Right:
@example
(defmacro foo ()
`(eval-when (:compile-toplevel :execute :load-toplevel) (really-foo)))
@end example
Adherence to this convention means that such @i{macros} behave
intuitively when appearing as @i{non-top-level forms}.
@item @t{*}
Placing a variable binding around an @b{eval-when} reliably
captures the binding because the compile-time-too mode cannot occur
(@i{i.e.}, introducing a variable binding means that the @b{eval-when}
is not a @i{top level form}).
For example,
@example
(let ((x 3))
(eval-when (:execute :load-toplevel :compile-toplevel) (print x)))
@end example
prints @t{3}
at execution (@i{i.e.}, load) time, and does not print anything at
compile time. This is important so that expansions of
@b{defun} and
@b{defmacro}
can be done in terms of @b{eval-when} and can correctly capture
the @i{lexical environment}.
@example
(defun bar (x) (defun foo () (+ x 3)))
@end example
might expand into
@example
(defun bar (x)
(progn (eval-when (:compile-toplevel)
(compiler::notice-function-definition 'foo '(x)))
(eval-when (:execute :load-toplevel)
(setf (symbol-function 'foo) #'(lambda () (+ x 3))))))
@end example
which would be treated by the above rules the same as
@example
(defun bar (x)
(setf (symbol-function 'foo) #'(lambda () (+ x 3))))
@end example
when the definition of @t{bar} is not a @i{top level form}.
@end table
@node load-time-value, quote, eval-when, Evaluation and Compilation Dictionary
@subsection load-time-value [Special Operator]
@code{load-time-value} @i{form {&optional} read-only-p} @result{} @i{object}
@subsubheading Arguments and Values::
@i{form}---a @i{form}; evaluated as described below.
@i{read-only-p}---a @i{boolean}; not evaluated.
@i{object}---the @i{primary value} resulting from evaluating @i{form}.
@subsubheading Description::
@b{load-time-value} provides a mechanism for delaying evaluation of @i{form}
until the expression is in the run-time environment; see @ref{Compilation}.
@i{Read-only-p} designates whether the result can be considered a
@i{constant object}.
If @b{t},
the result is a read-only quantity that can,
if appropriate to the @i{implementation},
be copied into read-only space and/or @i{coalesced} with @i{similar}
@i{constant objects} from other @i{programs}.
If @b{nil} (the default),
the result must be neither copied nor coalesced;
it must be considered to be potentially modifiable data.
If a @b{load-time-value} expression is processed by @b{compile-file},
the compiler performs its normal semantic processing (such as macro expansion
and translation into machine code) on @i{form}, but arranges for the
execution of @i{form} to occur at load time in a @i{null lexical environment},
with the result of this @i{evaluation} then being treated as
a @i{literal object}
at run time. It is guaranteed that the evaluation of @i{form}
will take place only once when the @i{file} is @i{loaded}, but
the order of evaluation with respect to the evaluation of
@i{top level forms} in the file is @i{implementation-dependent}.
@ITindex{order of evaluation}
@ITindex{evaluation order}
If a @b{load-time-value} expression appears within a function compiled
with @b{compile}, the @i{form} is evaluated at compile time in a
@i{null lexical environment}. The result of this compile-time evaluation
is treated as
a @i{literal object}
in the compiled code.
If a @b{load-time-value} expression is processed by @b{eval},
@i{form} is evaluated in a @i{null lexical environment},
and one value is returned. Implementations that implicitly compile
(or partially compile) expressions processed by @b{eval}
might evaluate @i{form} only once, at the time this compilation is performed.
If the @i{same} @i{list} @t{(load-time-value @i{form})} is
evaluated or compiled more than once, it is @i{implementation-dependent}
whether @i{form} is evaluated only once or is evaluated more than once.
This can happen both when an expression being evaluated or compiled shares
substructure, and when the @i{same} @i{form} is processed by @b{eval} or
@b{compile} multiple times.
Since a @b{load-time-value} expression can be
referenced in more than one place and can be evaluated multiple times
by @b{eval}, it is
@i{implementation-dependent} whether each execution returns
a fresh @i{object}
or returns the same @i{object} as some other execution.
Users must use caution when destructively modifying the resulting
@i{object}.
If two lists @t{(load-time-value @i{form})}
that are the @i{same} under @b{equal} but are not @i{identical}
are evaluated or compiled,
their values always come from distinct evaluations of @i{form}.
Their @i{values} may not be coalesced
unless @i{read-only-p} is @b{t}.
@subsubheading Examples::
@example
;;; The function INCR1 always returns the same value, even in different images.
;;; The function INCR2 always returns the same value in a given image,
;;; but the value it returns might vary from image to image.
(defun incr1 (x) (+ x #.(random 17)))
(defun incr2 (x) (+ x (load-time-value (random 17))))
;;; The function FOO1-REF references the nth element of the first of
;;; the *FOO-ARRAYS* that is available at load time. It is permissible for
;;; that array to be modified (e.g., by SET-FOO1-REF); FOO1-REF will see the
;;; updated values.
(defvar *foo-arrays* (list (make-array 7) (make-array 8)))
(defun foo1-ref (n) (aref (load-time-value (first *my-arrays*) nil) n))
(defun set-foo1-ref (n val)
(setf (aref (load-time-value (first *my-arrays*) nil) n) val))
;;; The function BAR1-REF references the nth element of the first of
;;; the *BAR-ARRAYS* that is available at load time. The programmer has
;;; promised that the array will be treated as read-only, so the system
;;; can copy or coalesce the array.
(defvar *bar-arrays* (list (make-array 7) (make-array 8)))
(defun bar1-ref (n) (aref (load-time-value (first *my-arrays*) t) n))
;;; This use of LOAD-TIME-VALUE permits the indicated vector to be coalesced
;;; even though NIL was specified, because the object was already read-only
;;; when it was written as a literal vector rather than created by a constructor.
;;; User programs must treat the vector v as read-only.
(defun baz-ref (n)
(let ((v (load-time-value #(A B C) nil)))
(values (svref v n) v)))
;;; This use of LOAD-TIME-VALUE permits the indicated vector to be coalesced
;;; even though NIL was specified in the outer situation because T was specified
;;; in the inner situation. User programs must treat the vector v as read-only.
(defun baz-ref (n)
(let ((v (load-time-value (load-time-value (vector 1 2 3) t) nil)))
(values (svref v n) v)))
@end example
@subsubheading See Also::
@ref{compile-file}
,
@ref{compile}
,
@ref{eval}
,
@ref{Minimal Compilation},
@ref{Compilation}
@subsubheading Notes::
@b{load-time-value} must appear outside of quoted structure in a
``for @i{evaluation}'' position. In situations which would appear to call
for use of @b{load-time-value} within a quoted structure,
the @i{backquote} @i{reader macro} is probably called for;
see @ref{Backquote}.
Specifying @b{nil} for @i{read-only-p} is not a way to force an object
to become modifiable if it has already been made read-only. It is only a way
to say that, for an object that is modifiable, this operation is not intended
to make that object read-only.
@node quote, compiler-macro-function, load-time-value, Evaluation and Compilation Dictionary
@subsection quote [Special Operator]
@code{quote} @i{object} @result{} @i{object}
@subsubheading Arguments and Values::
@i{object}---an @i{object}; not evaluated.
@subsubheading Description::
The @b{quote} @i{special operator} just returns @i{object}.
The consequences are undefined if @i{literal objects} (including
@i{quoted objects}) are destructively modified.
@subsubheading Examples::
@example
(setq a 1) @result{} 1
(quote (setq a 3)) @result{} (SETQ A 3)
a @result{} 1
'a @result{} A
''a @result{} (QUOTE A)
'''a @result{} (QUOTE (QUOTE A))
(setq a 43) @result{} 43
(list a (cons a 3)) @result{} (43 (43 . 3))
(list (quote a) (quote (cons a 3))) @result{} (A (CONS A 3))
1 @result{} 1
'1 @result{} 1
"foo" @result{} "foo"
'"foo" @result{} "foo"
(car '(a b)) @result{} A
'(car '(a b)) @result{} (CAR (QUOTE (A B)))
#(car '(a b)) @result{} #(CAR (QUOTE (A B)))
'#(car '(a b)) @result{} #(CAR (QUOTE (A B)))
@end example
@subsubheading See Also::
@ref{Evaluation},
@ref{Single-Quote},
@ref{Compiler Terminology}
@subsubheading Notes::
The textual notation @t{'@i{object}} is equivalent to @t{(quote @i{object})};
see @ref{Compiler Terminology}.
Some @i{objects}, called @i{self-evaluating objects},
do not require quotation by @b{quote}.
However, @i{symbols} and @i{lists} are used to represent parts of programs,
and so would not be useable as constant data in a program without @b{quote}.
Since @b{quote} suppresses the @i{evaluation} of these @i{objects},
they become data rather than program.
@node compiler-macro-function, define-compiler-macro, quote, Evaluation and Compilation Dictionary
@subsection compiler-macro-function [Accessor]
@code{compiler-macro-function} @i{name {&optional} environment} @result{} @i{function}
(setf (@code{ compiler-macro-function} @i{name {&optional} environment}) new-function)@*
@subsubheading Arguments and Values::
@i{name}---a @i{function name}.
@i{environment}---an @i{environment} @i{object}.
@i{function}, @i{new-function}---a @i{compiler macro function}, or @b{nil}.
@subsubheading Description::
@i{Accesses} the @i{compiler macro function} named @i{name}, if any,
in the @i{environment}.
A value of @b{nil} denotes the absence of a @i{compiler macro function} named @i{name}.
@subsubheading Exceptional Situations::
The consequences are undefined if @i{environment} is @i{non-nil}
in a use of @b{setf} of @b{compiler-macro-function}.
@subsubheading See Also::
@ref{define-compiler-macro}
, @ref{Compiler Macros}
@node define-compiler-macro, defmacro, compiler-macro-function, Evaluation and Compilation Dictionary
@subsection define-compiler-macro [Macro]
@code{define-compiler-macro} @i{name lambda-list {[[@{@i{declaration}@}{*} | @i{documentation}]]} @{@i{form}@}{*}}@*
@result{} @i{name}
@subsubheading Arguments and Values::
@i{name}---a @i{function name}.
@i{lambda-list}---a @i{macro lambda list}.
@i{declaration}---a @b{declare} @i{expression}; not evaluated.
@i{documentation}---a @i{string}; not evaluated.
@i{form}---a @i{form}.
@subsubheading Description::
[Editorial Note by KMP: This definition probably needs to be fully expanded to not
refer through the definition of defmacro, but should suffice for now.]
This is the normal mechanism for defining a @i{compiler macro function}.
Its manner of definition is the same as for @b{defmacro}; the only
differences are:
@table @asis
@item @t{*}
The @i{name} can be a @i{function name} naming
any @i{function} or @i{macro}.
@item @t{*}
The expander function is installed as a @i{compiler macro function}
for the @i{name}, rather than as a @i{macro function}.
@item @t{*}
The @b{&whole} argument is bound to the form argument that
is passed to the @i{compiler macro function}. The remaining lambda-list
parameters are specified as if this form contained the function name in the
@i{car} and the actual arguments in the @i{cdr}, but if the @i{car}
of the actual form is the symbol @b{funcall}, then the destructuring of
the arguments is actually performed using its @i{cddr} instead.
@item @t{*}
@i{Documentation} is attached as a @i{documentation string}
to @i{name} (as kind @b{compiler-macro})
and to the @i{compiler macro function}.
@item @t{*}
Unlike an ordinary @i{macro}, a @i{compiler macro}
can decline to provide an expansion merely by returning a form that is
the @i{same} as the original (which can be obtained by using
@b{&whole}).
@end table
@subsubheading Examples::
@example
(defun square (x) (expt x 2)) @result{} SQUARE
(define-compiler-macro square (&whole form arg)
(if (atom arg)
`(expt ,arg 2)
(case (car arg)
(square (if (= (length arg) 2)
`(expt ,(nth 1 arg) 4)
form))
(expt (if (= (length arg) 3)
(if (numberp (nth 2 arg))
`(expt ,(nth 1 arg) ,(* 2 (nth 2 arg)))
`(expt ,(nth 1 arg) (* 2 ,(nth 2 arg))))
form))
(otherwise `(expt ,arg 2))))) @result{} SQUARE
(square (square 3)) @result{} 81
(macroexpand '(square x)) @result{} (SQUARE X), @i{false}
(funcall (compiler-macro-function 'square) '(square x) nil)
@result{} (EXPT X 2)
(funcall (compiler-macro-function 'square) '(square (square x)) nil)
@result{} (EXPT X 4)
(funcall (compiler-macro-function 'square) '(funcall #'square x) nil)
@result{} (EXPT X 2)
(defun distance-positional (x1 y1 x2 y2)
(sqrt (+ (expt (- x2 x1) 2) (expt (- y2 y1) 2))))
@result{} DISTANCE-POSITIONAL
(defun distance (&key (x1 0) (y1 0) (x2 x1) (y2 y1))
(distance-positional x1 y1 x2 y2))
@result{} DISTANCE
(define-compiler-macro distance (&whole form
&rest key-value-pairs
&key (x1 0 x1-p)
(y1 0 y1-p)
(x2 x1 x2-p)
(y2 y1 y2-p)
&allow-other-keys
&environment env)
(flet ((key (n) (nth (* n 2) key-value-pairs))
(arg (n) (nth (1+ (* n 2)) key-value-pairs))
(simplep (x)
(let ((expanded-x (macroexpand x env)))
(or (constantp expanded-x env)
(symbolp expanded-x)))))
(let ((n (/ (length key-value-pairs) 2)))
(multiple-value-bind (x1s y1s x2s y2s others)
(loop for (key) on key-value-pairs by #'cddr
count (eq key ':x1) into x1s
count (eq key ':y1) into y1s
count (eq key ':x2) into x2s
count (eq key ':y1) into y2s
count (not (member key '(:x1 :x2 :y1 :y2)))
into others
finally (return (values x1s y1s x2s y2s others)))
(cond ((and (= n 4)
(eq (key 0) :x1)
(eq (key 1) :y1)
(eq (key 2) :x2)
(eq (key 3) :y2))
`(distance-positional ,x1 ,y1 ,x2 ,y2))
((and (if x1-p (and (= x1s 1) (simplep x1)) t)
(if y1-p (and (= y1s 1) (simplep y1)) t)
(if x2-p (and (= x2s 1) (simplep x2)) t)
(if y2-p (and (= y2s 1) (simplep y2)) t)
(zerop others))
`(distance-positional ,x1 ,y1 ,x2 ,y2))
((and (< x1s 2) (< y1s 2) (< x2s 2) (< y2s 2)
(zerop others))
(let ((temps (loop repeat n collect (gensym))))
`(let ,(loop for i below n
collect (list (nth i temps) (arg i)))
(distance
,@@(loop for i below n
append (list (key i) (nth i temps)))))))
(t form))))))
@result{} DISTANCE
(dolist (form
'((distance :x1 (setq x 7) :x2 (decf x) :y1 (decf x) :y2 (decf x))
(distance :x1 (setq x 7) :y1 (decf x) :x2 (decf x) :y2 (decf x))
(distance :x1 (setq x 7) :y1 (incf x))
(distance :x1 (setq x 7) :y1 (incf x) :x1 (incf x))
(distance :x1 a1 :y1 b1 :x2 a2 :y2 b2)
(distance :x1 a1 :x2 a2 :y1 b1 :y2 b2)
(distance :x1 a1 :y1 b1 :z1 c1 :x2 a2 :y2 b2 :z2 c2)))
(print (funcall (compiler-macro-function 'distance) form nil)))
@t{ |> } (LET ((#:G6558 (SETQ X 7))
@t{ |> } (#:G6559 (DECF X))
@t{ |> } (#:G6560 (DECF X))
@t{ |> } (#:G6561 (DECF X)))
@t{ |> } (DISTANCE :X1 #:G6558 :X2 #:G6559 :Y1 #:G6560 :Y2 #:G6561))
@t{ |> } (DISTANCE-POSITIONAL (SETQ X 7) (DECF X) (DECF X) (DECF X))
@t{ |> } (LET ((#:G6567 (SETQ X 7))
@t{ |> } (#:G6568 (INCF X)))
@t{ |> } (DISTANCE :X1 #:G6567 :Y1 #:G6568))
@t{ |> } (DISTANCE :X1 (SETQ X 7) :Y1 (INCF X) :X1 (INCF X))
@t{ |> } (DISTANCE-POSITIONAL A1 B1 A2 B2)
@t{ |> } (DISTANCE-POSITIONAL A1 B1 A2 B2)
@t{ |> } (DISTANCE :X1 A1 :Y1 B1 :Z1 C1 :X2 A2 :Y2 B2 :Z2 C2)
@result{} NIL
@end example
@subsubheading See Also::
@ref{compiler-macro-function}
,
@ref{defmacro}
,
@ref{documentation; (setf documentation)}
,
@ref{Syntactic Interaction of Documentation Strings and Declarations}
@subsubheading Notes::
The consequences of writing a @i{compiler macro} definition for a function
in the @t{COMMON-LISP} @i{package} are undefined; it is quite possible that in some
@i{implementations} such an attempt would override an equivalent or equally
important definition. In general, it is recommended that a programmer only
write @i{compiler macro} definitions for @i{functions} he or she personally
maintains--writing a @i{compiler macro} definition for a function maintained
elsewhere is normally considered a violation of traditional rules of modularity
and data abstraction.
@node defmacro, macro-function, define-compiler-macro, Evaluation and Compilation Dictionary
@subsection defmacro [Macro]
@code{defmacro} @i{name lambda-list {[[@{@i{declaration}@}{*} | @i{documentation}]]} @{@i{form}@}{*}}@*
@result{} @i{name}
@subsubheading Arguments and Values::
@i{name}---a @i{symbol}.
@i{lambda-list}---a @i{macro lambda list}.
@i{declaration}---a @b{declare} @i{expression}; not evaluated.
@i{documentation}---a @i{string}; not evaluated.
@i{form}---a @i{form}.
@subsubheading Description::
Defines @i{name} as a @i{macro}
by associating a @i{macro function} with that @i{name}
in the global environment.
The @i{macro function} is defined in the same @i{lexical environment}
in which the @b{defmacro} @i{form} appears.
The parameter variables in @i{lambda-list} are bound to
destructured portions of the macro call.
The expansion function
accepts two arguments, a @i{form} and an
@i{environment}. The expansion function returns a @i{form}.
The body of the expansion function is specified by @i{forms}.
@i{Forms} are executed in order. The value of the
last @i{form} executed is returned as the expansion of the
@i{macro}.
The body @i{forms} of the expansion function (but not the @i{lambda-list})
are implicitly enclosed in a @i{block} whose name is @i{name}.
The @i{lambda-list} conforms to the requirements described in @ref{Macro Lambda Lists}.
@i{Documentation} is attached as a @i{documentation string}
to @i{name} (as kind @b{function})
and to the @i{macro function}.
@b{defmacro} can be used to redefine a @i{macro} or to replace
a @i{function} definition with a @i{macro} definition.
Recursive expansion of the @i{form} returned must terminate,
including the expansion of other @i{macros} which are @i{subforms}
of other @i{forms} returned.
The consequences are undefined if the result of fully macroexpanding
a @i{form}
contains any @i{circular} @i{list structure} except in @i{literal objects}.
If a @b{defmacro} @i{form} appears as a @i{top level form},
the @i{compiler} must store the @i{macro} definition at compile time,
so that occurrences of the macro later on in the file can be expanded correctly.
Users must ensure that the body of the @i{macro} can be evaluated at
compile time if it is referenced within the @i{file} being @i{compiled}.
@subsubheading Examples::
@example
(defmacro mac1 (a b) "Mac1 multiplies and adds"
`(+ ,a (* ,b 3))) @result{} MAC1
(mac1 4 5) @result{} 19
(documentation 'mac1 'function) @result{} "Mac1 multiplies and adds"
(defmacro mac2 (&optional (a 2 b) (c 3 d) &rest x) `'(,a ,b ,c ,d ,x)) @result{} MAC2
(mac2 6) @result{} (6 T 3 NIL NIL)
(mac2 6 3 8) @result{} (6 T 3 T (8))
(defmacro mac3 (&whole r a &optional (b 3) &rest x &key c (d a))
`'(,r ,a ,b ,c ,d ,x)) @result{} MAC3
(mac3 1 6 :d 8 :c 9 :d 10) @result{} ((MAC3 1 6 :D 8 :C 9 :D 10) 1 6 9 8 (:D 8 :C 9 :D 10))
@end example
The stipulation that
an embedded @i{destructuring lambda list} is permitted only
where @i{ordinary lambda list} syntax would permit a parameter name
but not a @i{list} is made to prevent ambiguity. For example,
the following is not valid:
@example
(defmacro loser (x &optional (a b &rest c) &rest z)
...)
@end example
because @i{ordinary lambda list} syntax does permit a
@i{list} following @t{&optional};
the list @t{(a b &rest c)} would be interpreted as describing an
optional parameter named @t{a} whose default value is that of the
form @t{b}, with a supplied-p parameter named @b{&rest} (not valid),
and an extraneous symbol @t{c} in the list (also not valid). An almost
correct way to express this is
@example
(defmacro loser (x &optional ((a b &rest c)) &rest z)
...)
@end example
The extra set of parentheses removes the ambiguity. However, the
definition is now incorrect because a macro call such as @t{(loser (car pool))}
would not provide any argument form for the lambda list @t{(a b &rest c)},
and so the default value against which to match the @i{lambda list} would be
@b{nil} because no explicit default value was specified.
The consequences of this are unspecified
since the empty list, @b{nil}, does not have @i{forms} to satisfy the
parameters @t{a} and @t{b}. The fully correct definition would be either
@example
(defmacro loser (x &optional ((a b &rest c) '(nil nil)) &rest z)
...)
@end example
or
@example
(defmacro loser (x &optional ((&optional a b &rest c)) &rest z)
...)
@end example
These differ slightly: the first requires that if the macro call
specifies @t{a} explicitly then it must also specify @t{b} explicitly,
whereas the second does not have this requirement. For example,
@example
(loser (car pool) ((+ x 1)))
@end example
would be a valid call for the second definition but not for the first.
@example
(defmacro dm1a (&whole x) `',x)
(macroexpand '(dm1a)) @result{} (QUOTE (DM1A))
(macroexpand '(dm1a a)) is an error.
(defmacro dm1b (&whole x a &optional b) `'(,x ,a ,b))
(macroexpand '(dm1b)) is an error.
(macroexpand '(dm1b q)) @result{} (QUOTE ((DM1B Q) Q NIL))
(macroexpand '(dm1b q r)) @result{} (QUOTE ((DM1B Q R) Q R))
(macroexpand '(dm1b q r s)) is an error.
@end example
@example
(defmacro dm2a (&whole form a b) `'(form ,form a ,a b ,b))
(macroexpand '(dm2a x y)) @result{} (QUOTE (FORM (DM2A X Y) A X B Y))
(dm2a x y) @result{} (FORM (DM2A X Y) A X B Y)
(defmacro dm2b (&whole form a (&whole b (c . d) &optional (e 5))
&body f &environment env)
``(,',form ,,a ,',b ,',(macroexpand c env) ,',d ,',e ,',f))
;Note that because backquote is involved, implementations may differ
;slightly in the nature (though not the functionality) of the expansion.
(macroexpand '(dm2b x1 (((incf x2) x3 x4)) x5 x6))
@result{} (LIST* '(DM2B X1 (((INCF X2) X3 X4))
X5 X6)
X1
'((((INCF X2) X3 X4)) (SETQ X2 (+ X2 1)) (X3 X4) 5 (X5 X6))),
T
(let ((x1 5))
(macrolet ((segundo (x) `(cadr ,x)))
(dm2b x1 (((segundo x2) x3 x4)) x5 x6)))
@result{} ((DM2B X1 (((SEGUNDO X2) X3 X4)) X5 X6)
5 (((SEGUNDO X2) X3 X4)) (CADR X2) (X3 X4) 5 (X5 X6))
@end example
@subsubheading See Also::
@ref{define-compiler-macro}
,
@ref{destructuring-bind}
,
@ref{documentation; (setf documentation)}
,
@ref{macroexpand; macroexpand-1}
,
@b{*macroexpand-hook*},
@b{macrolet},
@ref{macro-function}
,
@ref{Evaluation},
@ref{Compilation},
@ref{Syntactic Interaction of Documentation Strings and Declarations}
@node macro-function, macroexpand, defmacro, Evaluation and Compilation Dictionary
@subsection macro-function [Accessor]
@code{macro-function} @i{symbol {&optional} environment} @result{} @i{function}
(setf (@code{ macro-function} @i{symbol {&optional} environment}) new-function)@*
@subsubheading Arguments and Values::
@i{symbol}---a @i{symbol}.
@i{environment}---an @i{environment} @i{object}.
@i{function}---a @i{macro function} or @b{nil}.
@i{new-function}---a @i{macro function}.
@subsubheading Description::
Determines whether @i{symbol} has a function definition
as a macro in the specified @i{environment}.
If so, the macro expansion function, a function of two arguments,
is returned. If @i{symbol} has no function definition
in the lexical environment @i{environment}, or its definition
is not a @i{macro}, @b{macro-function} returns @b{nil}.
It is possible for both @b{macro-function} and
@b{special-operator-p}
to return @i{true} of @i{symbol}. The @i{macro} definition must
be available for use by programs that understand only the standard
@r{Common Lisp} @i{special forms}.
@subsubheading Examples::
@example
(defmacro macfun (x) '(macro-function 'macfun)) @result{} MACFUN
(not (macro-function 'macfun)) @result{} @i{false}
@end example
@example
(macrolet ((foo (&environment env)
(if (macro-function 'bar env)
''yes
''no)))
(list (foo)
(macrolet ((bar () :beep))
(foo))))
@result{} (NO YES)
@end example
@subsubheading Affected By::
@t{(setf macro-function)}, @b{defmacro}, and @b{macrolet}.
@subsubheading Exceptional Situations::
The consequences are undefined if @i{environment} is @i{non-nil}
in a use of @b{setf} of @b{macro-function}.
@subsubheading See Also::
@ref{defmacro}
, @ref{Evaluation}
@subsubheading Notes::
@b{setf} can be used with @b{macro-function} to install
a @i{macro} as a symbol's global function definition:
@example
(setf (macro-function symbol) fn)
@end example
The value installed must be a @i{function} that accepts two arguments,
the entire macro call and an @i{environment},
and computes the expansion for that call.
Performing this operation causes @i{symbol} to have only that
macro definition as its global function definition; any previous
definition, whether as a @i{macro} or as a
@i{function}, is lost.
@node macroexpand, define-symbol-macro, macro-function, Evaluation and Compilation Dictionary
@subsection macroexpand, macroexpand-1 [Function]
@code{macroexpand} @i{form {&optional} env} @result{} @i{expansion, expanded-p}
@code{macroexpand-} @i{1} @result{} @i{form {&optional} env}
{expansion, expanded-p}
@subsubheading Arguments and Values::
@i{form}---a @i{form}.
@i{env}---an @i{environment} @i{object}.
The default is @b{nil}.
@i{expansion}---a @i{form}.
@i{expanded-p}---a @i{generalized boolean}.
@subsubheading Description::
@b{macroexpand} and @b{macroexpand-1} expand @i{macros}.
If @i{form} is a @i{macro form},
then @b{macroexpand-1} expands the @i{macro form} call once.
@b{macroexpand}
repeatedly expands @i{form} until it is no longer a @i{macro form}.
In effect, @b{macroexpand} calls @b{macroexpand-1} repeatedly
until the @i{secondary value} it returns is @b{nil}.
If @i{form} is a @i{macro form},
then the @i{expansion} is a @i{macro expansion}
and @i{expanded-p} is @i{true}.
Otherwise,
the @i{expansion} is the given @i{form}
and @i{expanded-p} is @i{false}.
Macro expansion is carried out as follows.
Once @b{macroexpand-1} has
determined that the @i{form} is a @i{macro form},
it obtains an appropriate expansion @i{function} for the
@i{macro} or @i{symbol macro}.
The value of
@b{*macroexpand-hook*} is
coerced to a @i{function} and
then called as a @i{function} of three arguments:
the expansion @i{function},
the @i{form},
and the @i{env}.
The @i{value} returned from this call is taken to be the expansion
of the @i{form}.
In addition to @i{macro} definitions in the global environment,
any local macro definitions established within @i{env} by @b{macrolet}
or @b{symbol-macrolet} are considered.
If only @i{form} is supplied as an argument,
then the environment is effectively null, and only global macro definitions
as established by @b{defmacro} are considered.
@i{Macro} definitions are shadowed by local @i{function} definitions.
@subsubheading Examples::
@example
(defmacro alpha (x y) `(beta ,x ,y)) @result{} ALPHA
(defmacro beta (x y) `(gamma ,x ,y)) @result{} BETA
(defmacro delta (x y) `(gamma ,x ,y)) @result{} EPSILON
(defmacro expand (form &environment env)
(multiple-value-bind (expansion expanded-p)
(macroexpand form env)
`(values ',expansion ',expanded-p))) @result{} EXPAND
(defmacro expand-1 (form &environment env)
(multiple-value-bind (expansion expanded-p)
(macroexpand-1 form env)
`(values ',expansion ',expanded-p))) @result{} EXPAND-1
;; Simple examples involving just the global environment
(macroexpand-1 '(alpha a b)) @result{} (BETA A B), @i{true}
(expand-1 (alpha a b)) @result{} (BETA A B), @i{true}
(macroexpand '(alpha a b)) @result{} (GAMMA A B), @i{true}
(expand (alpha a b)) @result{} (GAMMA A B), @i{true}
(macroexpand-1 'not-a-macro) @result{} NOT-A-MACRO, @i{false}
(expand-1 not-a-macro) @result{} NOT-A-MACRO, @i{false}
(macroexpand '(not-a-macro a b)) @result{} (NOT-A-MACRO A B), @i{false}
(expand (not-a-macro a b)) @result{} (NOT-A-MACRO A B), @i{false}
;; Examples involving lexical environments
(macrolet ((alpha (x y) `(delta ,x ,y)))
(macroexpand-1 '(alpha a b))) @result{} (BETA A B), @i{true}
(macrolet ((alpha (x y) `(delta ,x ,y)))
(expand-1 (alpha a b))) @result{} (DELTA A B), @i{true}
(macrolet ((alpha (x y) `(delta ,x ,y)))
(macroexpand '(alpha a b))) @result{} (GAMMA A B), @i{true}
(macrolet ((alpha (x y) `(delta ,x ,y)))
(expand (alpha a b))) @result{} (GAMMA A B), @i{true}
(macrolet ((beta (x y) `(epsilon ,x ,y)))
(expand (alpha a b))) @result{} (EPSILON A B), @i{true}
(let ((x (list 1 2 3)))
(symbol-macrolet ((a (first x)))
(expand a))) @result{} (FIRST X), @i{true}
(let ((x (list 1 2 3)))
(symbol-macrolet ((a (first x)))
(macroexpand 'a))) @result{} A, @i{false}
(symbol-macrolet ((b (alpha x y)))
(expand-1 b)) @result{} (ALPHA X Y), @i{true}
(symbol-macrolet ((b (alpha x y)))
(expand b)) @result{} (GAMMA X Y), @i{true}
(symbol-macrolet ((b (alpha x y))
(a b))
(expand-1 a)) @result{} B, @i{true}
(symbol-macrolet ((b (alpha x y))
(a b))
(expand a)) @result{} (GAMMA X Y), @i{true}
;; Examples of shadowing behavior
(flet ((beta (x y) (+ x y)))
(expand (alpha a b))) @result{} (BETA A B), @i{true}
(macrolet ((alpha (x y) `(delta ,x ,y)))
(flet ((alpha (x y) (+ x y)))
(expand (alpha a b)))) @result{} (ALPHA A B), @i{false}
(let ((x (list 1 2 3)))
(symbol-macrolet ((a (first x)))
(let ((a x))
(expand a)))) @result{} A, @i{false}
@end example
@subsubheading Affected By::
@b{defmacro},
@b{setf} of @b{macro-function},
@b{macrolet},
@b{symbol-macrolet}
@subsubheading See Also::
@b{*macroexpand-hook*},
@ref{defmacro}
,
@ref{setf; psetf}
of
@ref{macro-function}
,
@b{macrolet},
@ref{symbol-macrolet}
,
@ref{Evaluation}
@subsubheading Notes::
Neither @b{macroexpand} nor @b{macroexpand-1}
makes any explicit attempt to expand @i{macro forms} that are
either @i{subforms} of the @i{form}
or @i{subforms} of the @i{expansion}.
Such expansion might occur implicitly, however,
due to the semantics or implementation of the @i{macro function}.
@node define-symbol-macro, symbol-macrolet, macroexpand, Evaluation and Compilation Dictionary
@subsection define-symbol-macro [Macro]
@code{define-symbol-macro} @i{symbol expansion}@*
@result{} @i{symbol}
@subsubheading Arguments and Values::
@i{symbol}---a @i{symbol}.
@i{expansion}---a @i{form}.
@subsubheading Description::
Provides a mechanism for globally affecting the @i{macro expansion}
of the indicated @i{symbol}.
Globally establishes an expansion function for the @i{symbol macro}
named by @i{symbol}.
The only guaranteed property of an expansion @i{function} for a @i{symbol macro}
is that when it is applied to the @i{form} and the @i{environment} it returns
the correct expansion. (In particular, it is @i{implementation-dependent}
whether the expansion is conceptually stored in the expansion function,
the @i{environment}, or both.)
Each global reference to @i{symbol} (@i{i.e.}, not @i{shadowed}_2 by a
@i{binding} for a @i{variable} or @i{symbol macro} named by
the same @i{symbol}) is expanded by the normal macro expansion process;
see @ref{Symbols as Forms}.
The expansion of a @i{symbol macro} is subject to further @i{macro expansion}
in the same @i{lexical environment} as the @i{symbol macro} reference,
exactly analogous to normal @i{macros}.
The consequences are unspecified if a @b{special} declaration is made for
@i{symbol} while in the scope of this definition (@i{i.e.}, when it is not
@i{shadowed}_2 by a @i{binding} for a @i{variable}
or @i{symbol macro} named by the same @i{symbol}).
Any use of @b{setq} to set the value of
the @i{symbol}
while in the scope of this definition
is treated as if it were a @b{setf}.
@b{psetq} of @i{symbol}
is treated as if it were a @b{psetf}, and
@b{multiple-value-setq}
is treated as if it were a @b{setf} of @b{values}.
A @i{binding} for a @i{symbol macro} can be @i{shadowed}_2
by @b{let} or @b{symbol-macrolet}.
@subsubheading Examples::
@example
(defvar *things* (list 'alpha 'beta 'gamma)) @result{} *THINGS*
(define-symbol-macro thing1 (first *things*)) @result{} THING1
(define-symbol-macro thing2 (second *things*)) @result{} THING2
(define-symbol-macro thing3 (third *things*)) @result{} THING3
thing1 @result{} ALPHA
(setq thing1 'ONE) @result{} ONE
*things* @result{} (ONE BETA GAMMA)
(multiple-value-setq (thing2 thing3) (values 'two 'three)) @result{} TWO
thing3 @result{} THREE
*things* @result{} (ONE TWO THREE)
(list thing2 (let ((thing2 2)) thing2)) @result{} (TWO 2)
@end example
@subsubheading Exceptional Situations::
If @i{symbol} is already defined as a @i{global variable},
an error of @i{type} @b{program-error} is signaled.
@subsubheading See Also::
@ref{symbol-macrolet}
,
@ref{macroexpand; macroexpand-1}
@node symbol-macrolet, *macroexpand-hook*, define-symbol-macro, Evaluation and Compilation Dictionary
@subsection symbol-macrolet [Special Operator]
@code{symbol-macrolet} @i{@r{(}@{{(}symbol expansion@r{)}@}{*}@r{)}
@{@i{declaration}@}{*}
@{@i{form}@}{*}}@*
@result{} @i{@{@i{result}@}{*}}
@subsubheading Arguments and Values::
@i{symbol}---a @i{symbol}.
@i{expansion}---a @i{form}.
@i{declaration}---a @b{declare} @i{expression}; not evaluated.
@i{forms}---an @i{implicit progn}.
@i{results}---the @i{values} returned by the @i{forms}.
@subsubheading Description::
@b{symbol-macrolet} provides a mechanism for
affecting the @i{macro expansion} environment for @i{symbols}.
@b{symbol-macrolet} lexically establishes expansion functions
for each of the @i{symbol macros} named by @i{symbols}.
The only guaranteed property of an expansion @i{function} for a @i{symbol macro}
is that when it is applied to the @i{form} and the @i{environment} it returns
the correct expansion. (In particular, it is @i{implementation-dependent}
whether the expansion is conceptually stored in the expansion function,
the @i{environment}, or both.)
Each reference to @i{symbol} as a variable within the lexical @i{scope}
of @b{symbol-macrolet} is expanded by the normal macro expansion process;
see @ref{Symbols as Forms}.
The expansion of a symbol macro is subject to further macro expansion
in the same lexical environment as the symbol macro invocation, exactly
analogous to normal @i{macros}.
Exactly the same @i{declarations} are allowed as for @b{let}
with one exception: @b{symbol-macrolet} signals an error
if a @b{special} declaration names one of the @i{symbols}
being defined by @b{symbol-macrolet}.
When the @i{forms} of the @b{symbol-macrolet} form are expanded,
any use of @b{setq} to set the value of one of the specified variables
is treated as if it were a @b{setf}.
@b{psetq} of a @i{symbol} defined as a symbol macro
is treated as if it were a @b{psetf}, and
@b{multiple-value-setq}
is treated as if it were a @b{setf} of @b{values}.
The use of @b{symbol-macrolet} can be shadowed by @b{let}.
In other words, @b{symbol-macrolet} only substitutes for occurrences
of @i{symbol} that would be in the @i{scope} of a lexical binding of
@i{symbol} surrounding the @i{forms}.
@subsubheading Examples::
@example
;;; The following is equivalent to
;;; (list 'foo (let ((x 'bar)) x)),
;;; not
;;; (list 'foo (let (('foo 'bar)) 'foo))
(symbol-macrolet ((x 'foo))
(list x (let ((x 'bar)) x)))
@result{} (foo bar)
@i{NOT}@result{} (foo foo)
(symbol-macrolet ((x '(foo x)))
(list x))
@result{} ((FOO X))
@end example
@subsubheading Exceptional Situations::
If an attempt is made to bind a @i{symbol} that is defined as a @i{global variable},
an error of @i{type} @b{program-error} is signaled.
If @i{declaration} contains a @b{special} declaration
that names one of the @i{symbols} being bound by @b{symbol-macrolet},
an error of @i{type} @b{program-error} is signaled.
@subsubheading See Also::
@ref{with-slots}
,
@ref{macroexpand; macroexpand-1}
@subsubheading Notes::
The special form @b{symbol-macrolet} is the basic mechanism that is used to
implement @b{with-slots}.
If a @b{symbol-macrolet} @i{form} is a @i{top level form},
the @i{forms} are also processed as @i{top level forms}.
See @ref{File Compilation}.
@node *macroexpand-hook*, proclaim, symbol-macrolet, Evaluation and Compilation Dictionary
@subsection *macroexpand-hook* [Variable]
@subsubheading Value Type::
a @i{designator} for a @i{function} of three @i{arguments}:
a @i{macro function},
a @i{macro form},
and an @i{environment} @i{object}.
@subsubheading Initial Value::
a @i{designator} for a function that is equivalent to the @i{function} @b{funcall},
but that might have additional @i{implementation-dependent} side-effects.
@subsubheading Description::
Used as the expansion interface hook by @b{macroexpand-1} to
control the @i{macro expansion} process.
When a @i{macro form} is to be expanded,
this @i{function} is called with three arguments:
the @i{macro function},
the @i{macro form},
and the @i{environment} in which the @i{macro form} is to be expanded.
The @i{environment} @i{object} has @i{dynamic extent};
the consequences are undefined if the @i{environment} @i{object} is
referred to outside the @i{dynamic extent} of the macro expansion function.
@subsubheading Examples::
@example
(defun hook (expander form env)
(format t "Now expanding: ~S~
(funcall expander form env)) @result{} HOOK
(defmacro machook (x y) `(/ (+ ,x ,y) 2)) @result{} MACHOOK
(macroexpand '(machook 1 2)) @result{} (/ (+ 1 2) 2), @i{true}
(let ((*macroexpand-hook* #'hook)) (macroexpand '(machook 1 2)))
@t{ |> } Now expanding (MACHOOK 1 2)
@result{} (/ (+ 1 2) 2), @i{true}
@end example
@subsubheading See Also::
@ref{macroexpand; macroexpand-1}
, @b{macroexpand-1},
@ref{funcall}
, @ref{Evaluation}
@subsubheading Notes::
The net effect of the chosen initial value is to just invoke the
@i{macro function}, giving it the @i{macro form} and
@i{environment} as its two arguments.
Users or user programs can @i{assign} this @i{variable} to
customize or trace the @i{macro expansion} mechanism. Note, however,
that this @i{variable} is a global resource, potentially shared by
multiple @i{programs}; as such, if any two @i{programs} depend for
their correctness on the setting of this @i{variable}, those
@i{programs} may not be able to run in the same @i{Lisp image}.
For this reason, it is frequently best to confine its uses to debugging
situations.
Users who put their own function into @b{*macroexpand-hook*}
should consider saving the previous value of the hook, and calling that
value from their own.
@node proclaim, declaim, *macroexpand-hook*, Evaluation and Compilation Dictionary
@subsection proclaim [Function]
@code{proclaim} @i{declaration-specifier} @result{} @i{@i{implementation-dependent}}
@subsubheading Arguments and Values::
@i{declaration-specifier}---a @i{declaration specifier}.
@subsubheading Description::
@i{Establishes} the @i{declaration} specified by @i{declaration-specifier}
in the @i{global environment}.
Such a @i{declaration}, sometimes called a @i{global declaration}
or a @i{proclamation}, is always in force unless locally @i{shadowed}.
@i{Names} of @i{variables} and @i{functions} within
@i{declaration-specifier} refer to @i{dynamic variables}
and global @i{function} definitions, respectively.
Figure 3--22 shows a list of @i{declaration identifiers}
that can be used with @b{proclaim}.
@group
@noindent
@w{ declaration inline optimize type }
@w{ ftype notinline special }
@noindent
@w{ Figure 3--22: Global Declaration Specifiers}
@end group
An implementation is free to support other (@i{implementation-defined})
@i{declaration identifiers} as well.
@subsubheading Examples::
@example
(defun declare-variable-types-globally (type vars)
(proclaim `(type ,type ,@@vars))
type)
;; Once this form is executed, the dynamic variable *TOLERANCE*
;; must always contain a float.
(declare-variable-types-globally 'float '(*tolerance*))
@result{} FLOAT
@end example
@subsubheading See Also::
@ref{declaim}
,
@b{declare},
@ref{Compilation}
@subsubheading Notes::
Although the @i{execution} of a @b{proclaim} @i{form}
has effects that might affect compilation, the compiler does not make
any attempt to recognize and specially process @b{proclaim} @i{forms}.
A @i{proclamation} such as the following, even if a @i{top level form},
does not have any effect until it is executed:
@example
(proclaim '(special *x*))
@end example
If compile time side effects are desired, @b{eval-when} may be useful.
For example:
@example
(eval-when (:execute :compile-toplevel :load-toplevel)
(proclaim '(special *x*)))
@end example
In most such cases, however, it is preferrable to use @b{declaim} for
this purpose.
Since @b{proclaim} @i{forms} are ordinary @i{function forms},
@i{macro forms} can expand into them.
@node declaim, declare, proclaim, Evaluation and Compilation Dictionary
@subsection declaim [Macro]
@code{declaim} @i{@{@i{declaration-specifier}@}{*}} @result{} @i{@i{implementation-dependent}}
@subsubheading Arguments and Values::
@i{declaration-specifier}---a @i{declaration specifier}; not evaluated.
@subsubheading Description::
Establishes the @i{declarations} specified by the @i{declaration-specifiers}.
If a use of this macro appears as a @i{top level form} in a @i{file}
being processed by the @i{file compiler}, the proclamations are also made
at compile-time. As with other defining macros, it is unspecified whether or
not the compile-time side-effects of a @b{declaim} persist after the
@i{file} has been @i{compiled}.
@subsubheading Examples::
@subsubheading See Also::
@b{declare},
@ref{proclaim}
@node declare, ignore, declaim, Evaluation and Compilation Dictionary
@subsection declare [Symbol]
@subsubheading Syntax::
@code{declare} @i{@{@i{declaration-specifier}@}{*}}
@subsubheading Arguments::
@i{declaration-specifier}---a @i{declaration specifier}; not evaluated.
@subsubheading Description::
A @b{declare} @i{expression}, sometimes called a @i{declaration},
can occur only at the beginning of the bodies of certain @i{forms};
that is, it may be preceded only by other @b{declare} @i{expressions},
or by a @i{documentation string} if the context permits.
A @b{declare} @i{expression} can occur in a @i{lambda expression}
or in any of the @i{forms} listed in Figure 3--23.
@group
@noindent
@w{ defgeneric do-external-symbols prog }
@w{ define-compiler-macro do-symbols prog* }
@w{ define-method-combination dolist restart-case }
@w{ define-setf-expander dotimes symbol-macrolet }
@w{ defmacro flet with-accessors }
@w{ defmethod handler-case with-hash-table-iterator }
@w{ defsetf labels with-input-from-string }
@w{ deftype let with-open-file }
@w{ defun let* with-open-stream }
@w{ destructuring-bind locally with-output-to-string }
@w{ do macrolet with-package-iterator }
@w{ do* multiple-value-bind with-slots }
@w{ do-all-symbols pprint-logical-block }
@noindent
@w{ Figure 3--23: Standardized Forms In Which Declarations Can Occur }
@end group
A @b{declare} @i{expression} can only occur
where specified by the syntax of these @i{forms}.
The consequences of attempting to evaluate a @b{declare} @i{expression}
are undefined. In situations where such @i{expressions} can appear,
explicit checks are made for their presence and they are never actually evaluated;
it is for this reason that they
are called ``@b{declare} @i{expressions}''
rather than ``@b{declare} @i{forms}.''
@i{Macro forms} cannot expand into declarations;
@b{declare} @i{expressions} must appear as actual @i{subexpressions} of
the @i{form} to which they refer.
Figure 3--24 shows a list of @i{declaration identifiers}
that can be used with @b{declare}.
@group
@noindent
@w{ dynamic-extent ignore optimize }
@w{ ftype inline special }
@w{ ignorable notinline type }
@noindent
@w{ Figure 3--24: Local Declaration Specifiers}
@end group
An implementation is free to support other (@i{implementation-defined})
@i{declaration identifiers} as well.
@subsubheading Examples::
@example
(defun nonsense (k x z)
(foo z x) ;First call to foo
(let ((j (foo k x)) ;Second call to foo
(x (* k k)))
(declare (inline foo) (special x z))
(foo x j z))) ;Third call to foo
@end example
In this example,
the @b{inline} declaration applies
only to the third call to @t{foo}, but not to the first or second ones.
The @b{special} declaration of @t{x} causes @b{let}
to make a dynamic @i{binding} for @t{x}, and causes the reference to
@t{x}
in the body of @b{let} to be a dynamic reference.
The reference to @t{x} in the second call to @t{foo} is a local reference
to the second parameter of @t{nonsense}.
The reference to @t{x} in the first call to @t{foo} is a local
reference, not a @b{special} one. The @b{special} declaration of @t{z}
causes the reference to @t{z} in the
third
call
to @t{foo} to be a dynamic reference; it does not
refer to the parameter to @t{nonsense} named @t{z}, because that
parameter @i{binding} has not been declared to be @b{special}.
(The @b{special} declaration of @t{z} does not appear in the body
of @b{defun}, but in an inner @i{form}, and therefore does not
affect the @i{binding} of the @i{parameter}.)
@subsubheading Exceptional Situations::
The consequences of trying to use a @b{declare} @i{expression} as
a @i{form} to be @i{evaluated} are undefined.
[Editorial Note by KMP: Probably we need to say something here about ill-formed
declare expressions.]
@subsubheading See Also::
@ref{proclaim}
,
@ref{Type Specifiers},
@b{declaration},
@b{dynamic-extent},
@b{ftype},
@b{ignorable},
@b{ignore},
@b{inline},
@b{notinline},
@b{optimize},
@b{type}
@node ignore, dynamic-extent, declare, Evaluation and Compilation Dictionary
@subsection ignore, ignorable [Declaration]
@subsubheading Syntax::
@t{@r{(}ignore @{@i{var} | @r{(}@b{function} @i{fn}@r{)}@}{*}@r{)}}
@t{@r{(}ignorable @{@i{var} | @r{(}@b{function} @i{fn}@r{)}@}{*}@r{)}}
@subsubheading Arguments::
@i{var}---a @i{variable} @i{name}.
@i{fn}---a @i{function} @i{name}.
@subsubheading Valid Context::
@i{declaration}
@subsubheading Binding Types Affected::
@i{variable}, @i{function}
@subsubheading Description::
The @b{ignore} and @b{ignorable} declarations
refer to @i{for-value} @i{references}
to @i{variable} @i{bindings} for the @i{vars}
and to @i{function} @i{bindings} for the @i{fns}.
An @b{ignore} @i{declaration} specifies that
@i{for-value} @i{references} to the indicated @i{bindings}
will not
occur within the scope of the @i{declaration}.
Within the @i{scope} of such a @i{declaration},
it is desirable
for a compiler to issue a warning about
the presence of
either a @i{for-value} @i{reference} to any @i{var} or @i{fn},
or a @b{special} @i{declaration} for any @i{var}.
An @b{ignorable} @i{declaration} specifies that
@i{for-value} @i{references} to the indicated @i{bindings}
might or might not
occur within the scope of the @i{declaration}.
Within the @i{scope} of such a @i{declaration},
it is not desirable
for a compiler to issue a warning about
the presence or absence of
either a @i{for-value} @i{reference} to any @i{var} or @i{fn},
or a @b{special} @i{declaration} for any @i{var}.
When not within the @i{scope}
of a @b{ignore} or @b{ignorable} @i{declaration},
it is desirable
for a compiler to issue a warning about
any @i{var} for which there is
neither a @i{for-value} @i{reference}
nor a @b{special} @i{declaration},
or about
any @i{fn} for which there is
no @i{for-value} @i{reference}.
Any warning about a ``used'' or ``unused'' @i{binding} must be of @i{type} @b{style-warning},
and may not affect program semantics.
The @i{stream variables} established by
@b{with-open-file},
@b{with-open-stream},
@b{with-input-from-string},
and @b{with-output-to-string},
and all @i{iteration variables} are, by definition, always ``used''.
Using @t{(declare (ignore @i{v}))},
for such a @i{variable} @i{v} has unspecified consequences.
@subsubheading See Also::
@b{declare}
@node dynamic-extent, type, ignore, Evaluation and Compilation Dictionary
@subsection dynamic-extent [Declaration]
@subsubheading Syntax::
@t{(dynamic-extent [[@{@i{var}@}{*} |
@r{(}@b{function} @i{fn}@r{)}@r{*}]])}
@subsubheading Arguments::
@i{var}---a @i{variable} @i{name}.
@i{fn}---a @i{function} @i{name}.
@subsubheading Valid Context::
@i{declaration}
@subsubheading Binding Types Affected::
@i{variable}, @i{function}
@subsubheading Description::
In some containing @i{form}, @i{F}, this declaration
asserts for each @i{var_i} (which need not be bound by @i{F}),
and for each @i{value} @i{v_@{ij@}} that @i{var_i} takes on,
and for each @i{object} @i{x_@{ijk@}} that
is
an @i{otherwise inaccessible part} of @i{v_@{ij@}} at any time when
@i{v_@{ij@}}
becomes the value of @i{var_i},
that just after the execution of @i{F} terminates,
@i{x_@{ijk@}} is either @i{inaccessible}
(if @i{F} established a @i{binding} for @i{var_i})
or still an @i{otherwise inaccessible part} of the current value of
@i{var_i} (if @i{F} did not establish a @i{binding}
for @i{var_i}).
The same relation holds for each @i{fn_i},
except that the @i{bindings} are in the @i{function} @i{namespace}.
The compiler is permitted to use
this information in any way that is appropriate to the @i{implementation}
and that does not conflict with the semantics of @r{Common Lisp}.
@b{dynamic-extent} declarations can be @i{free declarations}
or @i{bound declarations}.
The @i{vars} and @i{fns} named in a @b{dynamic-extent}
declaration must not refer to @i{symbol macro} or @i{macro} bindings.
@subsubheading Examples::
Since stack allocation of the initial value entails knowing at the
@i{object}'s creation time that the @i{object} can be
@i{stack-allocated}, it is not generally useful to make a
@b{dynamic-extent} @i{declaration} for @i{variables}
which have no lexically apparent initial value.
For example, it is probably useful to write:
@example
(defun f ()
(let ((x (list 1 2 3)))
(declare (dynamic-extent x))
...))
@end example
This would permit those compilers that wish to do so to @i{stack allocate}
the list held by the local variable @t{x}. It is permissible,
but in practice probably not as useful, to write:
@example
(defun g (x) (declare (dynamic-extent x)) ...)
(defun f () (g (list 1 2 3)))
@end example
Most compilers would probably not @i{stack allocate} the @i{argument}
to @t{g} in @t{f} because it would be a modularity violation for the compiler
to assume facts about @t{g} from within @t{f}. Only an implementation that
was willing to be responsible for recompiling @t{f} if the definition of @t{g}
changed incompatibly could legitimately @i{stack allocate} the @i{list}
argument to @t{g} in @t{f}.
Here is another example:
@example
(declaim (inline g))
(defun g (x) (declare (dynamic-extent x)) ...)
(defun f () (g (list 1 2 3)))
(defun f ()
(flet ((g (x) (declare (dynamic-extent x)) ...))
(g (list 1 2 3))))
@end example
In the previous example, some compilers might determine that optimization was
possible and others might not.
A variant of this is the so-called ``stack allocated rest list''
that can be achieved (in implementations supporting the optimization) by:
@example
(defun f (&rest x)
(declare (dynamic-extent x))
...)
@end example
Note that although the initial value of @t{x} is not explicit, the @t{f}
function is responsible for assembling the list @t{x} from the passed arguments,
so the @t{f} function can be optimized by the compiler to construct a
@i{stack-allocated} list instead of a heap-allocated list in implementations
that support such.
In the following example,
@example
(let ((x (list 'a1 'b1 'c1))
(y (cons 'a2 (cons 'b2 (cons 'c2 nil)))))
(declare (dynamic-extent x y))
...)
@end example
The @i{otherwise inaccessible parts} of @t{x} are three
@i{conses}, and the @i{otherwise inaccessible parts}
of @t{y} are three other @i{conses}.
None of the symbols @t{a1}, @t{b1}, @t{c1}, @t{a2},
@t{b2}, @t{c2}, or @b{nil} is an
@i{otherwise inaccessible part} of @t{x} or @t{y} because each
is @i{interned} and hence @i{accessible} by the @i{package}
(or @i{packages}) in which it is @i{interned}.
However, if a freshly allocated @i{uninterned} @i{symbol} had
been used, it would have been an @i{otherwise inaccessible part} of
the @i{list} which contained it.
@example
;; In this example, the implementation is permitted to @i{stack allocate}
;; the list that is bound to X.
(let ((x (list 1 2 3)))
(declare (dynamic-extent x))
(print x)
:done)
@t{ |> } (1 2 3)
@result{} :DONE
;; In this example, the list to be bound to L can be @i{stack-allocated}.
(defun zap (x y z)
(do ((l (list x y z) (cdr l)))
((null l))
(declare (dynamic-extent l))
(prin1 (car l)))) @result{} ZAP
(zap 1 2 3)
@t{ |> } 123
@result{} NIL
;; Some implementations might open-code LIST-ALL-PACKAGES in a way
;; that permits using @i{stack allocation} of the list to be bound to L.
(do ((l (list-all-packages) (cdr l)))
((null l))
(declare (dynamic-extent l))
(let ((name (package-name (car l))))
(when (string-search "COMMON-LISP" name) (print name))))
@t{ |> } "COMMON-LISP"
@t{ |> } "COMMON-LISP-USER"
@result{} NIL
;; Some implementations might have the ability to @i{stack allocate}
;; rest lists. A declaration such as the following should be a cue
;; to such implementations that stack-allocation of the rest list
;; would be desirable.
(defun add (&rest x)
(declare (dynamic-extent x))
(apply #'+ x)) @result{} ADD
(add 1 2 3) @result{} 6
(defun zap (n m)
;; Computes (RANDOM (+ M 1)) at relative speed of roughly O(N).
;; It may be slow, but with a good compiler at least it
;; doesn't waste much heap storage. :-@}
(let ((a (make-array n)))
(declare (dynamic-extent a))
(dotimes (i n)
(declare (dynamic-extent i))
(setf (aref a i) (random (+ i 1))))
(aref a m))) @result{} ZAP
(< (zap 5 3) 3) @result{} @i{true}
@end example
The following are in error, since the value of @t{x} is used outside of its
@i{extent}:
@example
(length (list (let ((x (list 1 2 3))) ; Invalid
(declare (dynamic-extent x))
x)))
(progn (let ((x (list 1 2 3))) ; Invalid
(declare (dynamic-extent x))
x)
nil)
@end example
@subsubheading See Also::
@b{declare}
@subsubheading Notes::
The most common optimization is to @i{stack allocate} the
initial value of the @i{objects} named by the @i{vars}.
It is permissible for an implementation to simply ignore this declaration.
@node type, inline, dynamic-extent, Evaluation and Compilation Dictionary
@subsection type [Declaration]
@subsubheading Syntax::
@t{(type @i{typespec} @{@i{var}@}{*})}
@t{(@i{typespec} @{@i{var}@}{*})}
@subsubheading Arguments::
@i{typespec}---a @i{type specifier}.
@i{var}---a @i{variable} @i{name}.
@subsubheading Valid Context::
@i{declaration} or @i{proclamation}
@subsubheading Binding Types Affected::
@i{variable}
@subsubheading Description::
Affects
only variable @i{bindings} and specifies that the
@i{vars} take on
values only of the specified @i{typespec}.
In particular, values assigned to the variables by @b{setq},
as well as the initial values of the @i{vars} must be of
the specified @i{typespec}.
@b{type} declarations never apply to function @i{bindings} (see @b{ftype}).
A type declaration of a @i{symbol}
defined by @b{symbol-macrolet} is equivalent
to wrapping a @b{the}
expression around the expansion of that @i{symbol},
although the @i{symbol}'s @i{macro expansion} is not actually affected.
The meaning of a type declaration
is equivalent to changing each reference to
a variable (@i{var}) within the scope of the
declaration to @t{(the @i{typespec} @i{var})},
changing each expression assigned to the
variable (@i{new-value}) within the scope of the declaration to
@t{(the @i{typespec} @i{new-value})},
and executing
@t{(the @i{typespec} @i{var})} at the moment the scope of the declaration
is entered.
A @i{type} declaration is valid in all declarations. The interpretation
of a type declaration is as follows:
@table @asis
@item 1.
During the execution of any reference to the
declared variable within the scope of the declaration, the consequences
are
undefined
if
the value of the declared variable is not of the declared @i{type}.
@item 2.
During the execution of any
@b{setq} of the declared variable within the scope
of the declaration, the consequences are
undefined
if the newly assigned value of the
declared variable is not of the declared @i{type}.
@item 3.
At the moment the
scope of the declaration is entered, the consequences are
undefined
if the value of the
declared variable is not of the declared @i{type}.
@end table
A @i{type} declaration affects only variable references within
its scope.
If nested @i{type} declarations refer to the same variable,
then the value of the variable must be a member of the intersection of
the declared @i{types}.
If there is a local @t{type} declaration for a dynamic
variable, and there is also a global @t{type} proclamation for that same
variable, then the value of the variable within the scope of the local
declaration must be a member of the intersection of the two declared
@i{types}.
@b{type} declarations can be @i{free declarations}
or @i{bound declarations}.
A @i{symbol} cannot be both the name of a @i{type} and the name of a
declaration. Defining a @i{symbol} as the @i{name} of a @i{class},
@i{structure}, @i{condition}, or @i{type}, when the @i{symbol}
has been @i{declared} as a declaration name, or vice versa, signals an error.
Within the @i{lexical scope} of an @b{array} type declaration,
all references to @i{array} @i{elements} are assumed to satisfy the
@i{expressed array element type} (as opposed to the @i{upgraded array element type}).
A compiler can treat
the code within the scope of the @b{array} type declaration as if each
@i{access} of an @i{array} @i{element} were surrounded by an appropriate
@b{the} form.
@subsubheading Examples::
@example
(defun f (x y)
(declare (type fixnum x y))
(let ((z (+ x y)))
(declare (type fixnum z))
z)) @result{} F
(f 1 2) @result{} 3
;; The previous definition of F is equivalent to
(defun f (x y)
;; This declaration is a shorthand form of the TYPE declaration
(declare (fixnum x y))
;; To declare the type of a return value, it's not necessary to
;; create a named variable. A THE special form can be used instead.
(the fixnum (+ x y))) @result{} F
(f 1 2) @result{} 3
@end example
@example
(defvar *one-array* (make-array 10 :element-type '(signed-byte 5)))
(defvar *another-array* (make-array 10 :element-type '(signed-byte 8)))
(defun frob (an-array)
(declare (type (array (signed-byte 5) 1) an-array))
(setf (aref an-array 1) 31)
(setf (aref an-array 2) 127)
(setf (aref an-array 3) (* 2 (aref an-array 3)))
(let ((foo 0))
(declare (type (signed-byte 5) foo))
(setf foo (aref an-array 0))))
(frob *one-array*)
(frob *another-array*)
@end example
The above definition of @t{frob} is equivalent to:
@example
(defun frob (an-array)
(setf (the (signed-byte 5) (aref an-array 1)) 31)
(setf (the (signed-byte 5) (aref an-array 2)) 127)
(setf (the (signed-byte 5) (aref an-array 3))
(* 2 (the (signed-byte 5) (aref an-array 3))))
(let ((foo 0))
(declare (type (signed-byte 5) foo))
(setf foo (the (signed-byte 5) (aref an-array 0)))))
@end example
Given an implementation in which
@i{fixnums} are 29 bits but @b{fixnum} @i{arrays}
are upgraded to signed 32-bit @i{arrays},
the following
could be compiled with all @i{fixnum} arithmetic:
@example
(defun bump-counters (counters)
(declare (type (array fixnum *) bump-counters))
(dotimes (i (length counters))
(incf (aref counters i))))
@end example
@subsubheading See Also::
@b{declare},
@ref{declaim}
,
@ref{proclaim}
@subsubheading Notes::
@t{(@i{typespec} @{@i{var}@}{*})}
is an abbreviation for @t{(type @i{typespec} @{@i{var}@}{*})}.
A @b{type} declaration for the arguments to a function does not
necessarily imply anything about the type of the result. The following
function is not permitted to be compiled using @i{implementation-dependent}
@i{fixnum}-only arithmetic:
@example
(defun f (x y) (declare (fixnum x y)) (+ x y))
@end example
To see why, consider @t{(f most-positive-fixnum 1)}.
Common Lisp defines that @t{F} must return a @i{bignum} here, rather
than signal an error or produce a mathematically incorrect result.
If you have special knowledge such ``@i{fixnum} overflow'' cases will
not come up, you can declare the result value to be in the @i{fixnum}
range, enabling some compilers to use more efficient arithmetic:
@example
(defun f (x y)
(declare (fixnum x y))
(the fixnum (+ x y)))
@end example
Note, however, that in the three-argument case, because of the possibility
of an implicit intermediate value growing too large, the following will not
cause @i{implementation-dependent} @i{fixnum}-only arithmetic to be used:
@example
(defun f (x y)
(declare (fixnum x y z))
(the fixnum (+ x y z)))
@end example
To see why, consider @t{(f most-positive-fixnum 1 -1).}
Although the arguments and the result are all @i{fixnums}, an intermediate
value is not a @i{fixnum}. If it is important that
@i{implementation-dependent} @i{fixnum}-only arithmetic be selected
in @i{implementations} that provide it,
consider writing something like this instead:
@example
(defun f (x y)
(declare (fixnum x y z))
(the fixnum (+ (the fixnum (+ x y)) z)))
@end example
@node inline, ftype, type, Evaluation and Compilation Dictionary
@subsection inline, notinline [Declaration]
@subsubheading Syntax::
@t{(inline @{@i{function-name}@}{*})}
@t{(notinline @{@i{function-name}@}{*})}
@subsubheading Arguments::
@i{function-name}---a @i{function name}.
@subsubheading Valid Context::
@i{declaration} or @i{proclamation}
@subsubheading Binding Types Affected::
@i{function}
@subsubheading Description::
@b{inline} specifies that
it is desirable for the compiler to produce inline calls
to the @i{functions} named by @i{function-names};
that is, the code for a specified @i{function-name}
should be integrated into the calling routine, appearing ``in line''
in place of a procedure call.
A compiler is free to ignore this declaration.
@b{inline} declarations never apply to variable @i{bindings}.
If one of the @i{functions} mentioned has a lexically apparent local definition
(as made by @b{flet} or @b{labels}), then the declaration
applies to that local definition and not to the global function definition.
While no @i{conforming implementation} is required to perform inline expansion
of user-defined functions, those @i{implementations} that do attempt
to recognize the following paradigm:
To define a @i{function} @t{f} that is not @b{inline} by default
but for which @t{(declare (inline f))} will make @i{f} be locally inlined,
the proper definition sequence is:
@example
(declaim (inline f))
(defun f ...)
(declaim (notinline f))
@end example
The @b{inline} proclamation preceding the @b{defun} @i{form}
ensures that the @i{compiler} has the opportunity save the information
necessary for inline expansion, and the @b{notinline} proclamation
following the @b{defun} @i{form} prevents @t{f} from being expanded
inline everywhere.
@b{notinline} specifies that it is
undesirable to compile the @i{functions}
named by @i{function-names} in-line.
A compiler is not free to ignore this declaration;
calls to the specified functions must be implemented as out-of-line subroutine calls.
If one of the @i{functions}
mentioned has a lexically apparent local definition
(as made by @b{flet} or @b{labels}), then the declaration
applies to that local definition and not to the global function definition.
In the presence of a @i{compiler macro} definition for
@i{function-name}, a @b{notinline} declaration prevents that
@i{compiler macro} from being used.
An @b{inline} declaration may be used to encourage use of
@i{compiler macro} definitions. @b{inline} and @b{notinline}
declarations otherwise have no effect when the lexically visible definition
of @i{function-name} is a @i{macro} definition.
@b{inline} and @b{notinline} declarations can be @i{free declarations} or
@i{bound declarations}.
@b{inline} and @b{notinline} declarations of functions that
appear before the body of a
@b{flet}
or @b{labels}
@i{form} that defines that function are @i{bound declarations}.
Such declarations in other contexts are @i{free declarations}.
@subsubheading Examples::
@example
;; The globally defined function DISPATCH should be open-coded,
;; if the implementation supports inlining, unless a NOTINLINE
;; declaration overrides this effect.
(declaim (inline dispatch))
(defun dispatch (x) (funcall (get (car x) 'dispatch) x))
;; Here is an example where inlining would be encouraged.
(defun top-level-1 () (dispatch (read-command)))
;; Here is an example where inlining would be prohibited.
(defun top-level-2 ()
(declare (notinline dispatch))
(dispatch (read-command)))
;; Here is an example where inlining would be prohibited.
(declaim (notinline dispatch))
(defun top-level-3 () (dispatch (read-command)))
;; Here is an example where inlining would be encouraged.
(defun top-level-4 ()
(declare (inline dispatch))
(dispatch (read-command)))
@end example
@subsubheading See Also::
@b{declare},
@ref{declaim}
,
@ref{proclaim}
@node ftype, declaration, inline, Evaluation and Compilation Dictionary
@subsection ftype [Declaration]
@subsubheading Syntax::
@t{(ftype @i{type} @{@i{function-name}@}{*})}
@subsubheading Arguments::
@i{function-name}---a @i{function name}.
@i{type}---a @i{type specifier}.
@subsubheading Valid Context::
@i{declaration} or @i{proclamation}
@subsubheading Binding Types Affected::
@i{function}
@subsubheading Description::
Specifies that the @i{functions} named by @i{function-names} are of
the functional type @i{type}.
For example:
@example
(declare (ftype (function (integer list) t) ith)
(ftype (function (number) float) sine cosine))
@end example
If one of the @i{functions} mentioned has a lexically apparent local definition
(as made by @b{flet} or @b{labels}), then the declaration
applies to that local definition and not to the global function definition.
@b{ftype} declarations never apply to variable @i{bindings} (see @t{type}).
The lexically apparent bindings of @i{function-names} must not be
@i{macro} definitions. (This is because @b{ftype} declares the
functional definition of each @i{function name} to be of a particular
subtype of @b{function}, and @i{macros} do not denote
@i{functions}.)
@b{ftype}
declarations
can be @i{free declarations} or @i{bound declarations}.
@b{ftype} declarations of functions that appear before the body of a
@b{flet}
or @b{labels}
@i{form} that defines that function are @i{bound declarations}.
Such declarations in other contexts are @i{free declarations}.
@subsubheading See Also::
@b{declare},
@ref{declaim}
,
@ref{proclaim}
@node declaration, optimize, ftype, Evaluation and Compilation Dictionary
@subsection declaration [Declaration]
@subsubheading Syntax::
@t{(declaration @{@i{name}@}{*})}
@subsubheading Arguments::
@i{name}---a @i{symbol}.
@subsubheading Valid Context::
@i{proclamation} only
@subsubheading Description::
Advises the compiler that each @i{name} is a valid but potentially
non-standard declaration name. The purpose of this is to tell one
compiler not to issue warnings for declarations meant for another
compiler or other program processor.
@subsubheading Examples::
@example
(declaim (declaration author target-language target-machine))
(declaim (target-language ada))
(declaim (target-machine IBM-650))
(defun strangep (x)
(declare (author "Harry Tweeker"))
(member x '(strange weird odd peculiar)))
@end example
@subsubheading See Also::
@ref{declaim}
,
@ref{proclaim}
@node optimize, special, declaration, Evaluation and Compilation Dictionary
@subsection optimize [Declaration]
@subsubheading Syntax::
@t{(optimize @{@i{quality} | (@i{quality} @i{value})@}{*})}
@IRindex{compilation-speed}
@IRindex{debug}
@IRindex{safety}
@IRindex{space}
@IRindex{speed}
@subsubheading Arguments::
@i{quality}---an @i{optimize quality}.
@i{value}---one of the @i{integers} @t{0}, @t{1}, @t{2}, or @t{3}.
@subsubheading Valid Context::
@i{declaration} or @i{proclamation}
@subsubheading Description::
Advises the compiler that each @i{quality} should be given attention
according to the specified corresponding @i{value}.
Each @i{quality} must be a @i{symbol} naming an @i{optimize quality};
the names and meanings of the standard @i{optimize qualities} are shown in
Figure 3--25.
@group
@noindent
@w{ Name Meaning }
@w{ @b{compilation-speed} speed of the compilation process }
@w{ @b{debug} ease of debugging }
@w{ @b{safety} run-time error checking }
@w{ @b{space} both code size and run-time space }
@w{ @b{speed} speed of the object code }
@noindent
@w{ Figure 3--25: Optimize qualities }
@end group
There may be other, @i{implementation-defined} @i{optimize qualities}.
A @i{value} @t{0} means that the corresponding @i{quality} is totally
unimportant, and @t{3} that the @i{quality} is extremely important;
@t{1} and @t{2} are intermediate values, with @t{1} the
neutral value.
@t{(@i{quality} 3)} can be abbreviated to @i{quality}.
Note that @i{code} which has the optimization @t{(safety 3)},
or just @b{safety},
is called @i{safe} @i{code}.
The consequences are unspecified if a @i{quality} appears more than once
with @i{different} @i{values}.
@subsubheading Examples::
@example
(defun often-used-subroutine (x y)
(declare (optimize (safety 2)))
(error-check x y)
(hairy-setup x)
(do ((i 0 (+ i 1))
(z x (cdr z)))
((null z))
;; This inner loop really needs to burn.
(declare (optimize speed))
(declare (fixnum i))
))
@end example
@subsubheading See Also::
@b{declare},
@ref{declaim}
,
@ref{proclaim}
,
@ref{Declaration Scope}
@subsubheading Notes::
An @b{optimize} declaration never applies to either a @i{variable} or
a @i{function} @i{binding}. An @b{optimize} declaration can only
be a @i{free declaration}. For more information, see @ref{Declaration Scope}.
@node special, locally, optimize, Evaluation and Compilation Dictionary
@subsection special [Declaration]
@subsubheading Syntax::
@t{(special @{@i{var}@}{*})}
@subsubheading Arguments::
@i{var}---a @i{symbol}.
@subsubheading Valid Context::
@i{declaration} or @i{proclamation}
@subsubheading Binding Types Affected::
@i{variable}
@subsubheading Description::
Specifies that all of
the @i{vars} named are dynamic.
This specifier affects variable @i{bindings} and
affects references.
All variable @i{bindings} affected are made to be dynamic @i{bindings},
and affected variable references refer to the current dynamic
@i{binding}.
For example:
@example
(defun hack (thing *mod*) ;The binding of the parameter
(declare (special *mod*)) ; *mod* is visible to hack1,
(hack1 (car thing))) ; but not that of thing.
(defun hack1 (arg)
(declare (special *mod*)) ;Declare references to *mod*
;within hack1 to be special.
(if (atom arg) *mod*
(cons (hack1 (car arg)) (hack1 (cdr arg)))))
@end example
A @b{special} declaration does not affect inner @i{bindings}
of a @i{var}; the inner @i{bindings} implicitly shadow
a @b{special} declaration and must be explicitly re-declared to
be @b{special}.
@b{special} declarations never apply to function @i{bindings}.
@b{special} declarations can be either @i{bound declarations},
affecting both a binding and references, or @i{free declarations},
affecting only references, depending on whether the declaration is
attached to a variable binding.
When used in a @i{proclamation}, a @b{special}
@i{declaration specifier}
applies to all @i{bindings} as well as to all references of the
mentioned variables. For example, after
@example
(declaim (special x))
@end example
then in a function definition such as
@example
(defun example (x) ...)
@end example
the parameter @t{x} is bound as a dynamic variable
rather than as a lexical variable.
@subsubheading Examples::
@example
(defun declare-eg (y) ;this y is special
(declare (special y))
(let ((y t)) ;this y is lexical
(list y
(locally (declare (special y)) y)))) ;this y refers to the
;special binding of y
@result{} DECLARE-EG
(declare-eg nil) @result{} (T NIL)
@end example
@example
(setf (symbol-value 'x) 6)
(defun foo (x) ;a lexical binding of x
(print x)
(let ((x (1+ x))) ;a special binding of x
(declare (special x)) ;and a lexical reference
(bar))
(1+ x))
(defun bar ()
(print (locally (declare (special x))
x)))
(foo 10)
@t{ |> } 10
@t{ |> } 11
@result{} 11
@end example
@example
(setf (symbol-value 'x) 6)
(defun bar (x y) ;[1] 1st occurrence of x
(let ((old-x x) ;[2] 2nd occurrence of x -- same as 1st occurrence
(x y)) ;[3] 3rd occurrence of x
(declare (special x))
(list old-x x)))
(bar 'first 'second) @result{} (FIRST SECOND)
@end example
@example
(defun few (x &optional (y *foo*))
(declare (special *foo*))
...)
@end example
The reference to @t{*foo*}
in the first line of this example is not @b{special}
even though there is a @b{special} declaration in the second line.
@example
(declaim (special prosp)) @result{} @i{implementation-dependent}
(setq prosp 1 reg 1) @result{} 1
(let ((prosp 2) (reg 2)) ;the binding of prosp is special
(set 'prosp 3) (set 'reg 3) ;due to the preceding proclamation,
(list prosp reg)) ;whereas the variable reg is lexical
@result{} (3 2)
(list prosp reg) @result{} (1 3)
(declaim (special x)) ;x is always special.
(defun example (x y)
(declare (special y))
(let ((y 3) (x (* x 2)))
(print (+ y (locally (declare (special y)) y)))
(let ((y 4)) (declare (special y)) (foo x)))) @result{} EXAMPLE
@end example
In the contorted code above, the outermost and innermost @i{bindings} of
@t{y} are dynamic,
but the middle
binding is lexical. The two arguments to @t{+} are different,
one being the value, which is @t{3}, of the lexical variable
@t{y}, and the other being the value of the dynamic variable named @t{y}
(a @i{binding}
of which happens, coincidentally, to lexically surround it at
an outer level). All the @i{bindings}
of @t{x} and references to @t{x}
are dynamic, however, because of the proclamation that @t{x} is
always @b{special}.
@subsubheading See Also::
@ref{defparameter; defvar}
,
@b{defvar}
@node locally, the, special, Evaluation and Compilation Dictionary
@subsection locally [Special Operator]
@code{locally} @i{@{@i{declaration}@}{*} @{@i{form}@}{*}} @result{} @i{@{@i{result}@}{*}}
@subsubheading Arguments and Values::
@i{Declaration}---a @b{declare} @i{expression}; not evaluated.
@i{forms}---an @i{implicit progn}.
@i{results}---the @i{values} of the @i{forms}.
@subsubheading Description::
Sequentially evaluates a body of @i{forms}
in a @i{lexical environment} where the given @i{declarations} have effect.
@subsubheading Examples::
@example
(defun sample-function (y) ;this y is regarded as special
(declare (special y))
(let ((y t)) ;this y is regarded as lexical
(list y
(locally (declare (special y))
;; this next y is regarded as special
y))))
@result{} SAMPLE-FUNCTION
(sample-function nil) @result{} (T NIL)
(setq x '(1 2 3) y '(4 . 5)) @result{} (4 . 5)
;;; The following declarations are not notably useful in specific.
;;; They just offer a sample of valid declaration syntax using LOCALLY.
(locally (declare (inline floor) (notinline car cdr))
(declare (optimize space))
(floor (car x) (cdr y))) @result{} 0, 1
@end example
@example
;;; This example shows a definition of a function that has a particular set
;;; of OPTIMIZE settings made locally to that definition.
(locally (declare (optimize (safety 3) (space 3) (speed 0)))
(defun frob (w x y &optional (z (foo x y)))
(mumble x y z w)))
@result{} FROB
;;; This is like the previous example, except that the optimize settings
;;; remain in effect for subsequent definitions in the same compilation unit.
(declaim (optimize (safety 3) (space 3) (speed 0)))
(defun frob (w x y &optional (z (foo x y)))
(mumble x y z w))
@result{} FROB
@end example
@subsubheading See Also::
@b{declare}
@subsubheading Notes::
The @b{special} declaration may be used with @b{locally}
to affect references to, rather than @i{bindings} of, @i{variables}.
If a @b{locally} @i{form} is a @i{top level form}, the body @i{forms}
are also processed as @i{top level forms}. See @ref{File Compilation}.
@node the, special-operator-p, locally, Evaluation and Compilation Dictionary
@subsection the [Special Operator]
@code{the} @i{value-type form} @result{} @i{@{@i{result}@}{*}}
@subsubheading Arguments and Values::
@i{value-type}---a @i{type specifier}; not evaluated.
@i{form}---a @i{form}; evaluated.
@i{results}---the @i{values} resulting from the @i{evaluation} of @i{form}.
These @i{values} must conform to the @i{type} supplied by @i{value-type};
see below.
@subsubheading Description::
@b{the} specifies that the @i{values}_@{1a@} returned by @i{form}
are of the @i{types} specified by @i{value-type}.
The consequences are undefined if any @i{result}
is not of the declared type.
It is permissible for @i{form} to @i{yield} a different number of @i{values}
than are specified by @i{value-type}, provided that the values
for which @i{types} are declared are indeed of those @i{types}.
Missing values are treated as @b{nil} for the purposes of checking their @i{types}.
Regardless of number of @i{values} declared by @i{value-type},
the number of @i{values} returned by the @b{the} @i{special form} is the same as
the number of @i{values} returned by @i{form}.
@subsubheading Examples::
@example
(the symbol (car (list (gensym)))) @result{} #:G9876
(the fixnum (+ 5 7)) @result{} 12
(the (values) (truncate 3.2 2)) @result{} 1, 1.2
(the integer (truncate 3.2 2)) @result{} 1, 1.2
(the (values integer) (truncate 3.2 2)) @result{} 1, 1.2
(the (values integer float) (truncate 3.2 2)) @result{} 1, 1.2
(the (values integer float symbol) (truncate 3.2 2)) @result{} 1, 1.2
(the (values integer float symbol t null list)
(truncate 3.2 2)) @result{} 1, 1.2
(let ((i 100))
(declare (fixnum i))
(the fixnum (1+ i))) @result{} 101
(let* ((x (list 'a 'b 'c))
(y 5))
(setf (the fixnum (car x)) y)
x) @result{} (5 B C)
@end example
@subsubheading Exceptional Situations::
The consequences are undefined if
the @i{values} @i{yielded} by the @i{form}
are not of the @i{type} specified by @i{value-type}.
@subsubheading See Also::
@b{values}
@subsubheading Notes::
The @b{values} @i{type specifier} can be used to indicate the types
of @i{multiple values}:
@example
(the (values integer integer) (floor x y))
(the (values string t)
(gethash the-key the-string-table))
@end example
@b{setf} can be used with @b{the} type declarations.
In this case the declaration is transferred to the form that
specifies the new value. The resulting @b{setf} @i{form}
is then analyzed.
@node special-operator-p, constantp, the, Evaluation and Compilation Dictionary
@subsection special-operator-p [Function]
@code{special-operator-p} @i{symbol} @result{} @i{generalized-boolean}
@subsubheading Arguments and Values::
@i{symbol}---a @i{symbol}.
@i{generalized-boolean}---a @i{generalized boolean}.
@subsubheading Description::
Returns @i{true} if @i{symbol} is a @i{special operator};
otherwise, returns @i{false}.
@subsubheading Examples::
@example
(special-operator-p 'if) @result{} @i{true}
(special-operator-p 'car) @result{} @i{false}
(special-operator-p 'one) @result{} @i{false}
@end example
@subsubheading Exceptional Situations::
Should signal @b{type-error} if its argument is not a @i{symbol}.
@subsubheading Notes::
Historically, this function was called @t{special-form-p}. The name was
finally declared a misnomer and changed, since it returned true for
@i{special operators}, not @i{special forms}.
@node constantp, , special-operator-p, Evaluation and Compilation Dictionary
@subsection constantp [Function]
@code{constantp} @i{form {&optional} environment} @result{} @i{generalized-boolean}
@subsubheading Arguments and Values::
@i{form}---a @i{form}.
@i{environment}---an @i{environment} @i{object}.
The default is @b{nil}.
@i{generalized-boolean}---a @i{generalized boolean}.
@subsubheading Description::
Returns @i{true} if @i{form} can be determined
by the @i{implementation} to be a @i{constant form}
in the indicated @i{environment};
otherwise, it returns @i{false} indicating either
that the @i{form} is not a @i{constant form}
or that it cannot be determined whether or not @i{form} is a @i{constant form}.
The following kinds of @i{forms} are considered @i{constant forms}:
@table @asis
@item @t{*}
@i{Self-evaluating objects}
(such as @i{numbers},
@i{characters},
and the various kinds of @i{arrays})
are always considered @i{constant forms}
and must be recognized as such by @b{constantp}.
@item @t{*}
@i{Constant variables}, such as @i{keywords},
symbols defined by @r{Common Lisp} as constant (such as @b{nil}, @b{t}, and @b{pi}),
and symbols declared as constant by the user in the indicated @i{environment}
using @b{defconstant}
are always considered @i{constant forms}
and must be recognized as such by @b{constantp}.
@item @t{*}
@b{quote} @i{forms} are always considered @i{constant forms}
and must be recognized as such by @b{constantp}.
@item @t{*}
An @i{implementation} is permitted, but not required, to detect
additional @i{constant forms}. If it does, it is also permitted,
but not required, to make use of information in the @i{environment}.
Examples of @i{constant forms} for which @b{constantp} might
or might not return @i{true} are:
@t{(sqrt pi)},
@t{(+ 3 2)},
@t{(length '(a b c))},
and
@t{(let ((x 7)) (zerop x))}.
@end table
If an @i{implementation} chooses to make use of the @i{environment}
information, such actions as expanding @i{macros} or performing function
inlining are permitted to be used, but not required;
however, expanding @i{compiler macros} is not permitted.
@subsubheading Examples::
@example
(constantp 1) @result{} @i{true}
(constantp 'temp) @result{} @i{false}
(constantp ''temp)) @result{} @i{true}
(defconstant this-is-a-constant 'never-changing) @result{} THIS-IS-A-CONSTANT
(constantp 'this-is-a-constant) @result{} @i{true}
(constantp "temp") @result{} @i{true}
(setq a 6) @result{} 6
(constantp a) @result{} @i{true}
(constantp '(sin pi)) @result{} @i{implementation-dependent}
(constantp '(car '(x))) @result{} @i{implementation-dependent}
(constantp '(eql x x)) @result{} @i{implementation-dependent}
(constantp '(typep x 'nil)) @result{} @i{implementation-dependent}
(constantp '(typep x 't)) @result{} @i{implementation-dependent}
(constantp '(values this-is-a-constant)) @result{} @i{implementation-dependent}
(constantp '(values 'x 'y)) @result{} @i{implementation-dependent}
(constantp '(let ((a '(a b c))) (+ (length a) 6))) @result{} @i{implementation-dependent}
@end example
@subsubheading Affected By::
The state of the global environment (@i{e.g.}, which @i{symbols} have been
declared to be the @i{names} of @i{constant variables}).
@subsubheading See Also::
@ref{defconstant}
@c end of including dict-eval-compile
@c %**end of chapter
|