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@z --- t_codes.hweb ---
FWEB version 1.62 (September 25, 1998)
Based on version 0.5 of S. Levy's CWEB [copyright (C) 1987 Princeton University]
@x-----------------------------------------------------------------------------
@ If the first byte of a token is less than $|0200| \equiv |ID0|$, the
token occupies a single byte. Another way of saying this is that codes less
than $|0200| \equiv |0x80| \equiv |0177| \equiv 128 \equiv 2^7$ are 7-bit
ASCII codes that represent themselves. In particular, a single-character
identifier like~`|x|' will be a one-byte token, while all longer
identifiers will occupy two bytes. We shall use the macro |TOKEN1| to help
us test for such a token, as in `|if(TOKEN1(a))@;|\dots'.
Some of the 7-bit ASCII codes will not be present, however, so we can
use them for special purposes. The following symbolic names are used:
\yskip \hang |join| denotes the concatenation of adjacent items with no
space or line breaks allowed between them (the \.{@@\&} operation of \.{WEB}).
\hang |stringg| denotes the beginning or end of a string or verbatim
construction;
\hang |constant| denotes the beginning or end of a numerical constant.
@^ASCII code@>
@D stringg OCTAL(2) /* Extended ASCII alpha should not appear. (The funny
spelling is to avoid conflict with the VAX' \.{stdlib}.) */
@D constant OCTAL(3) // Numerical constant.
@D begin_Xmeta or_or
@D end_Xmeta star_star
@D cdir OCTAL(6) // Brackets compiler directive..
@D colon_colon OCTAL(11) // \Cpp\ and \Fortran--90: `$\WCF$'.
@D join OCTAL(177) // |ASCII| delete will not appear.
@d ID0 0200 // $128 =$ end of the 7-bit ASCII codes.
@d TOKEN1(a) ((a) < ID0) // Is |a|~a single-byte token?
@ Otherwise we make a sixteen-bit token by combining two consecutive
bytes~|a| and~|b|. If $|0200| <= a < |0250| \equiv |MOD0|$, then
$(a-|0200|) \times 2^8 + |b|$ corresponds to an identifier; we shall
introduce the macro |IDENTIFIER(a,b)| to perform this construction. (This
means that there must be fewer than 10,240 identifiers, since $|050|\times
2^8 = 10,240$.) If
$|0250<=a<0320| \equiv |MOD1|$, then $(a-|0250|) \times 2^8 +|b|$ points to a
module name.
(Thus, there must be fewer than 10,240 module names.)
Otherwise, i.e., if |0320<=a<0400|, then $(a-|0320|) \times 2^8 +|b|$ is
the number of the module in which the current replacement text appears. If
that number is~0 (i.e., if $|a| \equiv |MOD1|$ and $|b| \equiv 0$, we have
the |LINE_NUM| identifier, which signifies four more bytes of line-number
info upcoming.
Notice that these conventions allow more module numbers than module
names. Thus, we can use the tokens between~|0370| and~|0377| for other
purposes. For example, see the definition of |MACRO_ARGUMENT|.
@m MOD0 0250
@m MOD1 0320
@d MACRO_ARGUMENT 0377 /* See the related definition and discussion of
|MOD0|. */
@d BASE2 0400 /* |0xFF + 1 = 0x100 = 256| */
@d MODULE_NAME $EVAL((MOD0-0200)<<8) /* |024000= 10240 = (0250-0200)*0400| */
@d MODULE_NUM $EVAL((MOD1-0200)<<8) /* |050000 = 20480 = (0320-0200)*0400| */
@d LINE_NUM $EVAL(MOD1<<8)@&L /* |0150000==0320*0400| */
@d IDENTIFIER(left,right)
((sixteen_bits)( ((left)-ID0)*BASE2 + (sixteen_bits)(right) ))
/* Construct two-byte token out of its constituents. */
@d LEFT(a,id) ((eight_bits)(((a)/BASE2 + (id)))) /* Make left-hand byte out of
|sixteen_bits|. */
@d RIGHT(a) ((eight_bits)(((a) % BASE2))) /* Make right-hand byte. */
@ Control codes in \.{WEB} begin with `\.{@@}', and the next character
identifies the code. Some of these are of interest only to \.{WEAVE},
so \.{TANGLE} ignores them; the others are converted by \.{TANGLE} into
internal code numbers by the |control_code| table below. The ordering
of these internal code numbers has been chosen to simplify the program logic;
larger numbers are given to the control codes that denote more significant
milestones.
The following table shows the assignments:
$$\def\:{\char\count255\global\advance\count255 by 1}
\def\Hrule{\noalign{\hrule}}\def\HHrule{\noalign{\hrule height2pt}}
\def\Width{60pt}
\count255='40
\vbox{
\hbox{\hbox to \Width{\it\hfill0\/\hfill}%
\hbox to \Width{\it\hfill1\/\hfill}%
\hbox to \Width{\it\hfill2\/\hfill}%
\hbox to \Width{\it\hfill3\/\hfill}%
\hbox to \Width{\it\hfill4\/\hfill}%
\hbox to \Width{\it\hfill5\/\hfill}%
\hbox to \Width{\it\hfill6\/\hfill}%
\hbox to \Width{\it\hfill7\/\hfill}}
\vskip 4pt
\hrule
\def\!{\vrule height 10.5pt depth 4.5pt}
\halign{\hbox to 0pt{\hskip -24pt\WO{\~#}\hfill}&\!
\hbox to \Width{\hfill$#$\hfill\!}&
&\hbox to \Width{\hfill$#$\hfill\!}\cr
00&\\{ignore}&\WMM &\\{verbatim}&\\{force\_line}&\WW &** &\WCC &\\{bell}\cr\Hrule
01&\dots &\\{begin\_cmnt}&\\{lf} &\WPP &\\{ff} &\\{cr}
&\\{begin\_lang} &\\{begin\_meta} \cr\Hrule
02&\WGG &\WLS &\WLL &\.{.DOT.}&; &\WSR &\WSlSl &\\{end\_meta}
\cr\Hrule
03&\\{stmt\_label}&\WMG &\WI &\WL &\WNN &\WG &\WS &\WV \cr\HHrule
04& &\WR & &\# & &\WMOD &\amp & \cr\Hrule
05& & &\ast &+ & &- & &/ \cr\Hrule
06& & & & & & & & \cr\Hrule
07& & & & &< &= &> &? \cr\Hrule
10&\Wcp &\Wcm &\Wcs &\Wcv &\Wcd &\Wcx &\Wca &\Wco \cr\Hrule
11&\Wcg &\Wcl & & & & & & \cr\Hrule
12& & & & & & & & \cr\Hrule
13& & & & & & &\^ & \cr\Hrule
14& & & & & & & & \cr\Hrule
15& & & & & & & & \cr\Hrule
16& & & & & & & & \cr\Hrule
17& & & & &\WOR &\.{@@\$}&\.{@@\_},\WTL&\\{join}\cr\HHrule
20&\.{L$l$}&\.{C} &\.{R} &\.{N} &\.{M} &\.{X} & & \cr\Hrule
21&\WNP &\WNC &\.{\#<}&\WPtr &\WCC & & &
\cr\Hrule
22& & & & & & & & \cr\Hrule
23&\\{constant}&\\{stringg}&\\{identifier}&\.{@@\^}&\.{@@9} &\.{@@.} &\.{@@t} &\.{@@'} \cr\Hrule
24&\.{@@\&}&\.{@@,} &\.{@@\char'174}&\.{@@/} &\.{@@\#} &\.{@@+} &\.{@@;}& \cr\Hrule
25&\.{@@(} &\.{@@)} &\.{\ } &\\{copy\_mode}&\\{toggle\_output}&\.{@@e}&\.{@@:}&
\cr\Hrule
26& & &\.{@@!} & & &\.{@@0} &\.{@@1} &\.{@@2} \cr\Hrule
27&\.{@@f} &\.{@@\%}& & &\.{@@l} &\.{@@o} &\.{@@d} &\.{@@m} \cr\Hrule
30&\.{@@\#ifdef}&\.{@@\#ifndef}&\.{@@\#if}&\.{@@\#else}&\.{@@\#elif}&\.{@@\#endif}
&\.{@@\#pragma} &\.{@@\#undef}\cr\Hrule
31&\.{@@a} &\.{@@<} &\.{@@\ }& & & & & \cr\Hrule
32& & & & & & & & \cr\Hrule
33& & & & & & & & \cr\Hrule
34& & & & & & & &
\cr\Hrule
35& & & & & & & &
\cr\Hrule
36& & & & & & & &
\cr\Hrule
37& & & & & & &\\{begin\_cmnt0}& \cr}
\hrule width 480pt}$$
@D ignore 0 // Control code of no interest to \.{TANGLE}.
@d begin_comment0 HEX(FE) // Sent from |input_ln|; marker for long comment.
@d begin_comment1 HEX(FD) // As above; marker for short comment.
@D module_number OCTAL(201) // Code returned by |get_output| for mod.\ numbers.
@D identifier OCTAL(202) // Code returned by |get_output| for identifiers.
@D id_keyword OCTAL(203) // As above, but for expandable keyword.
@D L_switch OCTAL(257) // Control code for `\.{@@L}'.
@D begin_FORTRAN OCTAL(260)
@D begin_RATFOR OCTAL(261)
@D begin_C OCTAL(262)
@D begin_LITERAL OCTAL(263)
@D verbatim OCTAL(264) /* Can't be~|02| as for \.{fweave}, because
|stringg| is defined to be that. */
@D invisible_cmnt OCTAL(265) // Control code for `\.{@@\%}'.
@D compiler_directive OCTAL(266) // No longer used.
@D Compiler_Directive OCTAL(267) // Control code for `\.{@@?}'.
@D keyword_name OCTAL(270) // Control code for `\.{@@k}'.
@D no_index OCTAL(300) // Control code for `\.{@@-}'.
@D yes_index OCTAL(301) // Control code for `\.{@@+}'.
@D ascii_constant OCTAL(302) // Control code for `\.{@@'}'.
@D begin_vcmnt OCTAL(303) // Control code for `\.{@@\slashstar}'.
@D big_line_break OCTAL(304) // Control code for `\.{@@\#}'.
@D begin_bp OCTAL(305)
@D insert_bp OCTAL(306)
@D begin_meta OCTAL(17) // Control code for |"@@("|.
@D end_meta OCTAL(27)
@D TeX_string OCTAL(307)
@D xref_roman OCTAL(310)
@D xref_typewriter OCTAL(311)
@D xref_wildcard OCTAL(312)
@D control_text OCTAL(313) // Control code for `\.{@@t}', `\.{@@\^}', etc.
@D begin_nuweb OCTAL(314)
@D no_mac_expand OCTAL(315) // Control code for `\.{@@\~}'
@D set_line_info OCTAL(316) // Expt'l control code for `\.{@@Q}'.
@D short_fcn OCTAL(317) // Control code for `\.{@@\lb}'.
@D formatt OCTAL(320) // Control code for `\.{@@f}'.
@D limbo_text OCTAL(323) // Control code for `\.{@@l}'.
@D op_def OCTAL(324) // Control code for `\.{@@v}'.
@D macro_def OCTAL(325) // Control code for `\.{@@W}'.
@D ignore_defn OCTAL(327)// Stuff to here should be ignored when scanning defn.
@D new_output_file OCTAL(331) // Control code for `\.{@@o}'.
@D definition OCTAL(332) // Control code for `\.{@@d}'.
@D undefinition OCTAL(333) // Control code for `\.{@@u}'.
@D WEB_definition OCTAL(334) // Control code for `\.{@@m}'.
@D m_ifdef OCTAL(335)
@D m_ifndef OCTAL(336)
@D m_if OCTAL(337)
@D m_else OCTAL(340)
@D m_elif OCTAL(341)
@D m_endif OCTAL(342)
@D m_for OCTAL(343)
@D m_endfor OCTAL(344)
@D m_line OCTAL(345)
@D m_undef OCTAL(346)
@D end_of_buffer OCTAL(347)
@D begin_code OCTAL(350) // Control code for `\.{@@a}'.
@D module_name OCTAL(351) // Control code for `\.{@@<}'.
@D new_module OCTAL(352) // Control code for `\.{@@\ }' and `\.{@@*}'.
|
