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
|
<!DOCTYPE html>
<html lang="en" dir="ltr" class="client-nojs">
<head>
<title>std::promise - cppreference.com</title>
<meta charset="UTF-8" />
<meta name="generator" content="MediaWiki 1.21.2" />
<link rel="alternate" type="application/x-wiki" title="Edit" href="http://en.cppreference.com/mwiki/index.php?title=cpp/thread/promise&action=edit" />
<link rel="edit" title="Edit" href="http://en.cppreference.com/mwiki/index.php?title=cpp/thread/promise&action=edit" />
<link rel="shortcut icon" href="../../../favicon.ico" />
<link rel="search" type="application/opensearchdescription+xml" href="../../../mwiki/opensearch_desc.php" title="cppreference.com (en)" />
<link rel="EditURI" type="application/rsd+xml" href="http://en.cppreference.com/mwiki/api.php?action=rsd" />
<link rel="alternate" type="application/atom+xml" title="cppreference.com Atom feed" href="http://en.cppreference.com/mwiki/index.php?title=Special:RecentChanges&feed=atom" />
<link rel="stylesheet" href="../../../mwiki/load.php%3Fdebug=false&lang=en&modules=ext.gadget.ColiruCompiler%257Cext.rtlcite%257Cmediawiki.legacy.commonPrint%252Cshared%257Cskins.cppreference2&only=styles&skin=cppreference2&*.css" />
<meta name="ResourceLoaderDynamicStyles" content="" />
<link rel="stylesheet" href="../../../mwiki/load.php%3Fdebug=false&lang=en&modules=site&only=styles&skin=cppreference2&*.css" />
<style>a:lang(ar),a:lang(ckb),a:lang(fa),a:lang(kk-arab),a:lang(mzn),a:lang(ps),a:lang(ur){text-decoration:none}#toc{display:none}.editsection{display:none}
/* cache key: mwiki1-mwiki_en_:resourceloader:filter:minify-css:7:472787eddcf4605d11de8c7ef047234f */</style>
<script src="../../../mwiki/load.php%3Fdebug=false&lang=en&modules=startup&only=scripts&skin=cppreference2&*"></script>
<script>if(window.mw){
mw.config.set({"wgCanonicalNamespace":"","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":0,"wgPageName":"cpp/thread/promise","wgTitle":"cpp/thread/promise","wgCurRevisionId":81978,"wgArticleId":2517,"wgIsArticle":true,"wgAction":"view","wgUserName":null,"wgUserGroups":["*"],"wgCategories":[],"wgBreakFrames":false,"wgPageContentLanguage":"en","wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"dmy","wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgMonthNamesShort":["","Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"],"wgRelevantPageName":"cpp/thread/promise","wgRestrictionEdit":[],"wgRestrictionMove":[]});
}</script><script>if(window.mw){
mw.loader.implement("user.options",function(){mw.user.options.set({"ccmeonemails":0,"cols":80,"date":"default","diffonly":0,"disablemail":0,"disablesuggest":0,"editfont":"default","editondblclick":0,"editsection":0,"editsectiononrightclick":0,"enotifminoredits":0,"enotifrevealaddr":0,"enotifusertalkpages":1,"enotifwatchlistpages":0,"extendwatchlist":0,"externaldiff":0,"externaleditor":0,"fancysig":0,"forceeditsummary":0,"gender":"unknown","hideminor":0,"hidepatrolled":0,"imagesize":2,"justify":0,"math":1,"minordefault":0,"newpageshidepatrolled":0,"nocache":0,"noconvertlink":0,"norollbackdiff":0,"numberheadings":0,"previewonfirst":0,"previewontop":1,"quickbar":5,"rcdays":7,"rclimit":50,"rememberpassword":0,"rows":25,"searchlimit":20,"showhiddencats":0,"showjumplinks":1,"shownumberswatching":1,"showtoc":0,"showtoolbar":1,"skin":"cppreference2","stubthreshold":0,"thumbsize":2,"underline":2,"uselivepreview":0,"usenewrc":0,"watchcreations":0,"watchdefault":0,"watchdeletion":0,
"watchlistdays":3,"watchlisthideanons":0,"watchlisthidebots":0,"watchlisthideliu":0,"watchlisthideminor":0,"watchlisthideown":0,"watchlisthidepatrolled":0,"watchmoves":0,"wllimit":250,"variant":"en","language":"en","searchNs0":true,"searchNs1":false,"searchNs2":false,"searchNs3":false,"searchNs4":false,"searchNs5":false,"searchNs6":false,"searchNs7":false,"searchNs8":false,"searchNs9":false,"searchNs10":false,"searchNs11":false,"searchNs12":false,"searchNs13":false,"searchNs14":false,"searchNs15":false,"gadget-ColiruCompiler":1});;},{},{});mw.loader.implement("user.tokens",function(){mw.user.tokens.set({"editToken":"+\\","patrolToken":false,"watchToken":false});;},{},{});
/* cache key: mwiki1-mwiki_en_:resourceloader:filter:minify-js:7:ca03345b1e2c4d90a25d968753a73b92 */
}</script>
<script>if(window.mw){
mw.loader.load(["mediawiki.page.startup","mediawiki.legacy.wikibits","mediawiki.legacy.ajax"]);
}</script>
<style type="text/css">/*<![CDATA[*/
.source-cpp {line-height: normal;}
.source-cpp li, .source-cpp pre {
line-height: normal; border: 0px none white;
}
/**
* GeSHi Dynamically Generated Stylesheet
* --------------------------------------
* Dynamically generated stylesheet for cpp
* CSS class: source-cpp, CSS id:
* GeSHi (C) 2004 - 2007 Nigel McNie, 2007 - 2008 Benny Baumann
* (http://qbnz.com/highlighter/ and http://geshi.org/)
* --------------------------------------
*/
.cpp.source-cpp .de1, .cpp.source-cpp .de2 {font: normal normal 1em/1.2em monospace; margin:0; padding:0; background:none; vertical-align:top;}
.cpp.source-cpp {font-family:monospace;}
.cpp.source-cpp .imp {font-weight: bold; color: red;}
.cpp.source-cpp li, .cpp.source-cpp .li1 {font-weight: normal; vertical-align:top;}
.cpp.source-cpp .ln {width:1px;text-align:right;margin:0;padding:0 2px;vertical-align:top;}
.cpp.source-cpp .li2 {font-weight: bold; vertical-align:top;}
.cpp.source-cpp .kw1 {color: #0000dd;}
.cpp.source-cpp .kw2 {color: #0000ff;}
.cpp.source-cpp .kw3 {color: #0000dd;}
.cpp.source-cpp .kw4 {color: #0000ff;}
.cpp.source-cpp .co1 {color: #909090;}
.cpp.source-cpp .co2 {color: #339900;}
.cpp.source-cpp .coMULTI {color: #ff0000; font-style: italic;}
.cpp.source-cpp .es0 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es1 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es2 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es3 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es4 {color: #008000; font-weight: bold;}
.cpp.source-cpp .es5 {color: #008000; font-weight: bold;}
.cpp.source-cpp .br0 {color: #008000;}
.cpp.source-cpp .sy0 {color: #008000;}
.cpp.source-cpp .sy1 {color: #000080;}
.cpp.source-cpp .sy2 {color: #000040;}
.cpp.source-cpp .sy3 {color: #000040;}
.cpp.source-cpp .sy4 {color: #008080;}
.cpp.source-cpp .st0 {color: #008000;}
.cpp.source-cpp .nu0 {color: #000080;}
.cpp.source-cpp .nu6 {color: #000080;}
.cpp.source-cpp .nu8 {color: #000080;}
.cpp.source-cpp .nu12 {color: #000080;}
.cpp.source-cpp .nu16 {color:#000080;}
.cpp.source-cpp .nu17 {color:#000080;}
.cpp.source-cpp .nu18 {color:#000080;}
.cpp.source-cpp .nu19 {color:#000080;}
.cpp.source-cpp .ln-xtra, .cpp.source-cpp li.ln-xtra, .cpp.source-cpp div.ln-xtra {background-color: #ffc;}
.cpp.source-cpp span.xtra { display:block; }
/*]]>*/
</style><style type="text/css">/*<![CDATA[*/
.source-text {line-height: normal;}
.source-text li, .source-text pre {
line-height: normal; border: 0px none white;
}
/**
* GeSHi Dynamically Generated Stylesheet
* --------------------------------------
* Dynamically generated stylesheet for text
* CSS class: source-text, CSS id:
* GeSHi (C) 2004 - 2007 Nigel McNie, 2007 - 2008 Benny Baumann
* (http://qbnz.com/highlighter/ and http://geshi.org/)
* --------------------------------------
*/
.text.source-text .de1, .text.source-text .de2 {font: normal normal 1em/1.2em monospace; margin:0; padding:0; background:none; vertical-align:top;}
.text.source-text {font-family:monospace;}
.text.source-text .imp {font-weight: bold; color: red;}
.text.source-text li, .text.source-text .li1 {font-weight: normal; vertical-align:top;}
.text.source-text .ln {width:1px;text-align:right;margin:0;padding:0 2px;vertical-align:top;}
.text.source-text .li2 {font-weight: bold; vertical-align:top;}
.text.source-text .ln-xtra, .text.source-text li.ln-xtra, .text.source-text div.ln-xtra {background-color: #ffc;}
.text.source-text span.xtra { display:block; }
/*]]>*/
</style><!--[if lt IE 7]><style type="text/css">body{behavior:url("/mwiki/skins/cppreference2/csshover.min.htc")}</style><![endif]--></head>
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_thread_promise skin-cppreference2 action-view cpp-navbar">
<!-- header -->
<div id="mw-head" class="noprint">
<div id="cpp-head-first-base">
<div id="cpp-head-first">
<h5><a href="../../../index.html">
cppreference.com </a></h5>
<div id="cpp-head-search">
<!-- 0 -->
<div id="p-search">
<h5><label for="searchInput">Search</label></h5>
<form action="http://en.cppreference.com/mwiki/index.php" id="searchform">
<input type='hidden' name="title" value="Special:Search"/>
<div id="simpleSearch">
<input name="search" title="Search cppreference.com [f]" accesskey="f" id="searchInput" /> <button type="submit" name="button" title="Search the pages for this text" id="searchButton"><img src="../../../mwiki/skins/cppreference2/images/search-ltr.png%3F303" alt="Search" /></button> </div>
</form>
</div>
<!-- /0 -->
</div>
<div id="cpp-head-personal">
<!-- 0 -->
<div id="p-personal" class="">
<span id="pt-createaccount"><a href="http://en.cppreference.com/mwiki/index.php?title=Special:UserLogin&returnto=cpp%2Fthread%2Fpromise&type=signup">Create account</a></span> <div class="menu">
<ul>
<li id="pt-login"><a href="http://en.cppreference.com/mwiki/index.php?title=Special:UserLogin&returnto=cpp%2Fthread%2Fpromise" title="You are encouraged to log in; however, it is not mandatory [o]" accesskey="o">Log in</a></li> </ul>
</div>
</div>
<!-- /0 -->
</div>
</div>
</div>
<div id="cpp-head-second-base">
<div id="cpp-head-second">
<div id="cpp-head-tools-left">
<!-- 0 -->
<div id="p-namespaces" class="vectorTabs">
<h5>Namespaces</h5>
<ul>
<li id="ca-nstab-main" class="selected"><span><a href="promise.html" title="View the content page [c]" accesskey="c">Page</a></span></li>
<li id="ca-talk" class="new"><span><a href="http://en.cppreference.com/mwiki/index.php?title=Talk:cpp/thread/promise&action=edit&redlink=1" title="Discussion about the content page [t]" accesskey="t">Discussion</a></span></li>
</ul>
</div>
<!-- /0 -->
<!-- 1 -->
<div id="p-variants" class="vectorMenu emptyPortlet">
<h5><span>Variants</span><a href="promise.html#"></a></h5>
<div class="menu">
<ul>
</ul>
</div>
</div>
<!-- /1 -->
</div>
<div id="cpp-head-tools-right">
<!-- 0 -->
<div id="p-views" class="vectorTabs">
<h5>Views</h5>
<ul>
<li id="ca-view" class="selected"><span><a href="promise.html" >View</a></span></li>
<li id="ca-edit"><span><a href="http://en.cppreference.com/mwiki/index.php?title=cpp/thread/promise&action=edit" title="You can edit this page. Please use the preview button before saving [e]" accesskey="e">Edit</a></span></li>
<li id="ca-history" class="collapsible"><span><a href="http://en.cppreference.com/mwiki/index.php?title=cpp/thread/promise&action=history" title="Past revisions of this page [h]" accesskey="h">History</a></span></li>
</ul>
</div>
<!-- /0 -->
<!-- 1 -->
<div id="p-cactions" class="vectorMenu emptyPortlet">
<h5><span>Actions</span><a href="promise.html#"></a></h5>
<div class="menu">
<ul>
</ul>
</div>
</div>
<!-- /1 -->
</div>
</div>
</div>
</div>
<!-- /header -->
<!-- content -->
<div id="cpp-content-base">
<div id="content">
<a id="top"></a>
<div id="mw-js-message" style="display:none;"></div>
<!-- firstHeading -->
<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>promise</h1>
<!-- /firstHeading -->
<!-- bodyContent -->
<div id="bodyContent">
<!-- tagline -->
<div id="siteSub">From cppreference.com</div>
<!-- /tagline -->
<!-- subtitle -->
<div id="contentSub"><span class="subpages">< <a href="../../cpp.html" title="cpp">cpp</a>‎ | <a href="../thread.html" title="cpp/thread">thread</a></span></div>
<!-- /subtitle -->
<!-- bodycontent -->
<div id="mw-content-text" lang="en" dir="ltr" class="mw-content-ltr"><div class="t-navbar" style=""><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="../../cpp.html" title="cpp"> C++</a><div class="t-navbar-menu"><div><div><table class="t-nv-begin" cellpadding="0" style="line-height:1.1em;">
<tr class="t-nv"><td colspan="5"> <a href="../language.1.html" title="cpp/language"> Language</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../header.html" title="cpp/header"> Standard library headers</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../concept.html" title="cpp/concept"> Concepts</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../utility.html" title="cpp/utility"> Utilities library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../string.html" title="cpp/string"> Strings library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../container.html" title="cpp/container"> Containers library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../algorithm.html" title="cpp/algorithm"> Algorithms library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../iterator.html" title="cpp/iterator"> Iterators library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../numeric.html" title="cpp/numeric"> Numerics library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../io.html" title="cpp/io"> Input/output library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../locale.html" title="cpp/locale"> Localizations library</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../regex.html" title="cpp/regex"> Regular expressions library</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../atomic.html" title="cpp/atomic"> Atomic operations library</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../thread.html" title="cpp/thread"> Thread support library</a> <span class="t-mark-rev t-since-cxx11">(C++11)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../experimental.html" title="cpp/experimental"> Technical Specifications</a> </td></tr>
</table></div><div><span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/navbar_content&action=edit">[edit]</a></span></div></div></div></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="../thread.html" title="cpp/thread"> Thread support library</a><div class="t-navbar-menu"><div><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv-h1"><td colspan="5"> Threads</td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="thread.html" title="cpp/thread/thread"><span class="t-lines"><span>thread</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> <code>this_thread</code> namespace</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="get_id.html" title="cpp/thread/get id"><span class="t-lines"><span>get_id</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="yield.html" title="cpp/thread/yield"><span class="t-lines"><span>yield</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="sleep_for.html" title="cpp/thread/sleep for"><span class="t-lines"><span>sleep_for</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="sleep_until.html" title="cpp/thread/sleep until"><span class="t-lines"><span>sleep_until</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"> Mutual exclusion</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="mutex.html" title="cpp/thread/mutex"><span class="t-lines"><span>mutex</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="recursive_mutex.html" title="cpp/thread/recursive mutex"><span class="t-lines"><span>recursive_mutex</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="shared_mutex.html" title="cpp/thread/shared mutex"><span class="t-lines"><span>shared_mutex</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div></div></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="timed_mutex.html" title="cpp/thread/timed mutex"><span class="t-lines"><span>timed_mutex</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="recursive_timed_mutex.html" title="cpp/thread/recursive timed mutex"><span class="t-lines"><span>recursive_timed_mutex</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="shared_timed_mutex.html" title="cpp/thread/shared timed mutex"><span class="t-lines"><span>shared_timed_mutex</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx14">(C++14)</span></span></span></div></div></td></tr>
</table></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Generic lock management</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="lock_guard.html" title="cpp/thread/lock guard"><span class="t-lines"><span>lock_guard</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="unique_lock.html" title="cpp/thread/unique lock"><span class="t-lines"><span>unique_lock</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="shared_lock.html" title="cpp/thread/shared lock"><span class="t-lines"><span>shared_lock</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx14">(C++14)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="lock_tag_t.html" title="cpp/thread/lock tag t"><span class="t-lines"><span>defer_lock_t</span><span>try_to_lock_t</span><span>adopt_lock_t</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="lock.html" title="cpp/thread/lock"><span class="t-lines"><span>lock</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="try_lock.html" title="cpp/thread/try lock"><span class="t-lines"><span>try_lock</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="lock_tag.html" title="cpp/thread/lock tag"><span class="t-lines"><span>defer_lock</span><span>try_to_lock</span><span>adopt_lock</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="once_flag.html" title="cpp/thread/once flag"><span class="t-lines"><span>once_flag</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="call_once.html" title="cpp/thread/call once"><span class="t-lines"><span>call_once</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
</table></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"> Condition variables</td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="condition_variable.html" title="cpp/thread/condition variable"><span class="t-lines"><span>condition_variable</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="condition_variable_any.html" title="cpp/thread/condition variable any"><span class="t-lines"><span>condition_variable_any</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="notify_all_at_thread_exit.html" title="cpp/thread/notify all at thread exit"><span class="t-lines"><span>notify_all_at_thread_exit</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="cv_status.html" title="cpp/thread/cv status"><span class="t-lines"><span>cv_status</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv-h1"><td colspan="5"> Futures</td></tr>
<tr class="t-nv-col-table"><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><strong class="selflink"><span class="t-lines"><span>promise</span></span></strong></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="future.html" title="cpp/thread/future"><span class="t-lines"><span>future</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="shared_future.html" title="cpp/thread/shared future"><span class="t-lines"><span>shared_future</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="packaged_task.html" title="cpp/thread/packaged task"><span class="t-lines"><span>packaged_task</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="async.html" title="cpp/thread/async"><span class="t-lines"><span>async</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
</table></div></td><td><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="launch.html" title="cpp/thread/launch"><span class="t-lines"><span>launch</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="future_status.html" title="cpp/thread/future status"><span class="t-lines"><span>future_status</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="future_error.html" title="cpp/thread/future error"><span class="t-lines"><span>future_error</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="future_category.html" title="cpp/thread/future category"><span class="t-lines"><span>future_category</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="future_errc.html" title="cpp/thread/future errc"><span class="t-lines"><span>future_errc</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
</table></div></td></tr>
</table></div><div><span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/thread/navbar_content&action=edit">[edit]</a></span></div></div></div></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><strong class="selflink"><tt>std::promise</tt></strong><div class="t-navbar-menu"><div><div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv-h1"><td colspan="5"> Member functions</td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="promise/promise.html" title="cpp/thread/promise/promise"><span class="t-lines"><span>promise::promise</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="promise/~promise.html" title="cpp/thread/promise/~promise"><span class="t-lines"><span>promise::~promise</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="promise/operator=.html" title="cpp/thread/promise/operator="><span class="t-lines"><span>promise::operator=</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="promise/swap.html" title="cpp/thread/promise/swap"><span class="t-lines"><span>promise::swap</span></span></a></div></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Getting the result</td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="promise/get_future.html" title="cpp/thread/promise/get future"><span class="t-lines"><span>promise::get_future</span></span></a></div></div></td></tr>
<tr class="t-nv-h2"><td colspan="5"> Setting the result</td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="promise/set_value.html" title="cpp/thread/promise/set value"><span class="t-lines"><span>promise::set_value</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="promise/set_value_at_thread_exit.html" title="cpp/thread/promise/set value at thread exit"><span class="t-lines"><span>promise::set_value_at_thread_exit</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="promise/set_exception.html" title="cpp/thread/promise/set exception"><span class="t-lines"><span>promise::set_exception</span></span></a></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="promise/set_exception_at_thread_exit.html" title="cpp/thread/promise/set exception at thread exit"><span class="t-lines"><span>promise::set_exception_at_thread_exit</span></span></a></div></div></td></tr>
</table></div><div><span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/thread/promise/navbar_content&action=edit">[edit]</a></span></div></div></div></div><div class="t-navbar-sep"> </div></div>
<table class="t-dcl-begin"><tbody>
<tr class="t-dsc-header">
<td> <div>Defined in header <code><a href="../header/future.html" title="cpp/header/future"><future></a></code>
</div></td>
<td></td>
<td></td>
</tr>
<tr class="t-dcl t-since-cxx11">
<td> <div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> R <span class="sy1">></span> <span class="kw1">class</span> promise<span class="sy4">;</span></span></div></td>
<td> (1) </td>
<td> <span class="t-mark-rev t-since-cxx11">(since C++11)</span> </td>
</tr>
<tr class="t-dcl t-since-cxx11">
<td> <div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> R <span class="sy1">></span> <span class="kw1">class</span> promise<span class="sy1"><</span>R<span class="sy3">&</span><span class="sy1">></span><span class="sy4">;</span></span></div></td>
<td> (2) </td>
<td> <span class="t-mark-rev t-since-cxx11">(since C++11)</span> </td>
</tr>
<tr class="t-dcl t-since-cxx11">
<td> <div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><></span>          <span class="kw1">class</span> promise<span class="sy1"><</span><span class="kw4">void</span><span class="sy1">></span><span class="sy4">;</span></span></div></td>
<td> (3) </td>
<td> <span class="t-mark-rev t-since-cxx11">(since C++11)</span> </td>
</tr>
<tr class="t-dcl-sep"><td></td><td></td><td></td></tr>
</tbody></table>
<div class="t-li1"><span class="t-li">1)</span> base template</div>
<div class="t-li1"><span class="t-li">2)</span> non-void specialization, used to communicate objects between threads</div>
<div class="t-li1"><span class="t-li">3)</span> void specialization, used to communicate stateless events</div>
<p>The class template <code>std::promise</code> provides a facility to store a value or an exception that is later acquired asynchronously via a <span class="t-lc">std::future</span> object created by the <code>std::promise</code> object.
</p><p>Each promise is associated with a <i>shared state</i>, which contains some state information and a <i>result</i> which may be not yet evaluated, evaluated to a value (possibly void) or evaluated to an exception. A promise may do three things with the shared state:
</p>
<ul><li> <i>make ready</i>: the promise stores the result or the exception in the shared state. Marks the state ready and unblocks any thread waiting on a future associated with the shared state.
</li><li> <i>release</i>: the promise gives up its reference to the shared state. If this was the last such reference, the shared state is destroyed. Unless this was a shared state created by <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="async.html"><span class="kw1861">std::<span class="me2">async</span></span></a></span></span> which is not yet ready, this operation does not block.
</li><li> <i>abandon</i>: the promise stores the exception of type <span class="t-lc">std::future_error</span> with error code <span class="t-lc">std::future_errc::broken_promise</span>, makes the shared state <i>ready</i>, and then <i>releases</i> it.
</li></ul>
<p>The promise is the "push" end of the promise-future communication channel: the operation that stores a value in the shared state <i>synchronizes-with</i> (as defined in <span class="t-lc">std::memory_order</span>) the successful return from any function that is waiting on the shared state (such as <span class="t-lc">std::future::get</span>). Concurrent access to the same shared state may conflict otherwise: for example multiple callers of <span class="t-lc">std::shared_future::get</span> must either all be read-only or provide external synchronization.
</p>
<table id="toc" class="toc"><tr><td><div id="toctitle"><h2>Contents</h2></div>
<ul>
<li class="toclevel-1 tocsection-1"><a href="promise.html#Member_functions"><span class="tocnumber">1</span> <span class="toctext">Member functions</span></a>
<ul>
<li class="toclevel-2"><a href="promise.html#Getting_the_result"><span class="tocnumber">1.1</span> <span class="toctext">Getting the result</span></a></li>
<li class="toclevel-2"><a href="promise.html#Setting_the_result"><span class="tocnumber">1.2</span> <span class="toctext">Setting the result</span></a></li>
</ul>
</li>
<li class="toclevel-1 tocsection-2"><a href="promise.html#Non-member_functions"><span class="tocnumber">2</span> <span class="toctext">Non-member functions</span></a></li>
<li class="toclevel-1 tocsection-3"><a href="promise.html#Helper_classes"><span class="tocnumber">3</span> <span class="toctext">Helper classes</span></a></li>
<li class="toclevel-1 tocsection-4"><a href="promise.html#Example"><span class="tocnumber">4</span> <span class="toctext">Example</span></a></li>
</ul>
</td></tr></table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/thread/promise&action=edit&section=1" title="Edit section: Member functions">edit</a>]</span> <span class="mw-headline" id="Member_functions">Member functions</span></h3>
<table class="t-dsc-begin">
<tr class="t-dsc">
<td> <div class="t-dsc-member-div t-dsc-member-nobold-div"><div><a href="promise/promise.html" title="cpp/thread/promise/promise"> <span class="t-lines"><span>(constructor)</span></span></a></div></div>
</td>
<td> constructs the promise object <br /> <span class="t-mark">(public member function)</span> <span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/thread/promise/dsc_constructor&action=edit">[edit]</a></span>
</td></tr>
<tr class="t-dsc">
<td> <div class="t-dsc-member-div t-dsc-member-nobold-div"><div><a href="promise/~promise.html" title="cpp/thread/promise/~promise"> <span class="t-lines"><span>(destructor)</span></span></a></div></div>
</td>
<td> destructs the promise object <br /> <span class="t-mark">(public member function)</span> <span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/thread/promise/dsc_destructor&action=edit">[edit]</a></span>
</td></tr>
<tr class="t-dsc">
<td> <div class="t-dsc-member-div"><div><a href="promise/operator=.html" title="cpp/thread/promise/operator="> <span class="t-lines"><span>operator=</span></span></a></div></div>
</td>
<td> assigns the shared state <br /> <span class="t-mark">(public member function)</span> <span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/thread/promise/dsc_operator%3D&action=edit">[edit]</a></span>
</td></tr>
<tr class="t-dsc">
<td> <div class="t-dsc-member-div"><div><a href="promise/swap.html" title="cpp/thread/promise/swap"> <span class="t-lines"><span>swap</span></span></a></div></div>
</td>
<td> swaps two promise objects <br /> <span class="t-mark">(public member function)</span> <span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/thread/promise/dsc_swap&action=edit">[edit]</a></span>
</td></tr>
<tr>
<td colspan="2"> <h5> <span class="mw-headline" id="Getting_the_result"> Getting the result </span></h5>
</td></tr>
<tr class="t-dsc">
<td> <div class="t-dsc-member-div"><div><a href="promise/get_future.html" title="cpp/thread/promise/get future"> <span class="t-lines"><span>get_future</span></span></a></div></div>
</td>
<td> returns a <a href="future.html" title="cpp/thread/future"><tt>future</tt></a> associated with the promised result <br /> <span class="t-mark">(public member function)</span> <span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/thread/promise/dsc_get_future&action=edit">[edit]</a></span>
</td></tr>
<tr>
<td colspan="2"> <h5> <span class="mw-headline" id="Setting_the_result"> Setting the result </span></h5>
</td></tr>
<tr class="t-dsc">
<td> <div class="t-dsc-member-div"><div><a href="promise/set_value.html" title="cpp/thread/promise/set value"> <span class="t-lines"><span>set_value</span></span></a></div></div>
</td>
<td> sets the result to specific value <br /> <span class="t-mark">(public member function)</span> <span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/thread/promise/dsc_set_value&action=edit">[edit]</a></span>
</td></tr>
<tr class="t-dsc">
<td> <div class="t-dsc-member-div"><div><a href="promise/set_value_at_thread_exit.html" title="cpp/thread/promise/set value at thread exit"> <span class="t-lines"><span>set_value_at_thread_exit</span></span></a></div></div>
</td>
<td> sets the result to specific value while delivering the notification only at thread exit <br /> <span class="t-mark">(public member function)</span> <span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/thread/promise/dsc_set_value_at_thread_exit&action=edit">[edit]</a></span>
</td></tr>
<tr class="t-dsc">
<td> <div class="t-dsc-member-div"><div><a href="promise/set_exception.html" title="cpp/thread/promise/set exception"> <span class="t-lines"><span>set_exception</span></span></a></div></div>
</td>
<td> sets the result to indicate an exception <br /> <span class="t-mark">(public member function)</span> <span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/thread/promise/dsc_set_exception&action=edit">[edit]</a></span>
</td></tr>
<tr class="t-dsc">
<td> <div class="t-dsc-member-div"><div><a href="promise/set_exception_at_thread_exit.html" title="cpp/thread/promise/set exception at thread exit"> <span class="t-lines"><span>set_exception_at_thread_exit</span></span></a></div></div>
</td>
<td> sets the result to indicate an exception while delivering the notification only at thread exit <br /> <span class="t-mark">(public member function)</span> <span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/thread/promise/dsc_set_exception_at_thread_exit&action=edit">[edit]</a></span>
</td></tr>
</table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/thread/promise&action=edit&section=2" title="Edit section: Non-member functions">edit</a>]</span> <span class="mw-headline" id="Non-member_functions">Non-member functions</span></h3>
<table class="t-dsc-begin">
<tr class="t-dsc">
<td> <div class="t-dsc-member-div"><div><a href="promise/swap2.html" title="cpp/thread/promise/swap2"> <span class="t-lines"><span>std::swap<span class="t-dsc-small">(std::promise)</span></span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div>
</td>
<td> specializes the <span class="t-lc">std::swap</span> algorithm <br /> <span class="t-mark">(function template)</span> <span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/thread/promise/dsc_swap2&action=edit">[edit]</a></span>
</td></tr>
</table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/thread/promise&action=edit&section=3" title="Edit section: Helper classes">edit</a>]</span> <span class="mw-headline" id="Helper_classes">Helper classes</span></h3>
<table class="t-dsc-begin">
<tr class="t-dsc">
<td> <div class="t-dsc-member-div"><div><a href="promise/uses_allocator.html" title="cpp/thread/promise/uses allocator"> <span class="t-lines"><span>std::uses_allocator<span class="t-dsc-small"><std::promise></span></span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div>
</td>
<td> specializes the <span class="t-lc">std::uses_allocator</span> type trait <br /> <span class="t-mark">(class template specialization)</span> <span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/thread/promise/dsc_uses_allocator&action=edit">[edit]</a></span>
</td></tr>
</table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/thread/promise&action=edit&section=4" title="Edit section: Example">edit</a>]</span> <span class="mw-headline" id="Example">Example</span></h3>
<div class="t-example"><p>
<p>This example shows how <code>promise<int></code> can be used as signals between threads.
</p>
</p><div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co2">#include <vector></span>
<span class="co2">#include <thread></span>
<span class="co2">#include <future></span>
<span class="co2">#include <numeric></span>
<span class="co2">#include <iostream></span>
 
<span class="kw4">void</span> accumulate<span class="br0">(</span><a href="../container/vector.html"><span class="kw1094">std::<span class="me2">vector</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span><span class="sy4">::</span><span class="me2">iterator</span> first,
<a href="../container/vector.html"><span class="kw1094">std::<span class="me2">vector</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span><span class="sy4">::</span><span class="me2">iterator</span> last,
std<span class="sy4">::</span><span class="me2">promise</span><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span> accumulate_promise<span class="br0">)</span>
<span class="br0">{</span>
<span class="kw4">int</span> sum <span class="sy1">=</span> <a href="../algorithm/accumulate.html"><span class="kw1383">std::<span class="me2">accumulate</span></span></a><span class="br0">(</span>first, last, <span class="nu0">0</span><span class="br0">)</span><span class="sy4">;</span>
accumulate_promise.<span class="me1">set_value</span><span class="br0">(</span>sum<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// Notify future</span>
<span class="br0">}</span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="../container/vector.html"><span class="kw1094">std::<span class="me2">vector</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span> numbers <span class="sy1">=</span> <span class="br0">{</span> <span class="nu0">1</span>, <span class="nu0">2</span>, <span class="nu0">3</span>, <span class="nu0">4</span>, <span class="nu0">5</span>, <span class="nu0">6</span> <span class="br0">}</span><span class="sy4">;</span>
std<span class="sy4">::</span><span class="me2">promise</span><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span> accumulate_promise<span class="sy4">;</span>
<a href="future.html"><span class="kw1857">std::<span class="me2">future</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span> accumulate_future <span class="sy1">=</span> accumulate_promise.<span class="me1">get_future</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<a href="thread.html"><span class="kw1826">std::<span class="me2">thread</span></span></a> work_thread<span class="br0">(</span>accumulate, numbers.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, numbers.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span>,
std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>accumulate_promise<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
accumulate_future.<span class="me1">wait</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// wait for result</span>
<a href="../io/cout.html"><span class="kw1481">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"result="</span> <span class="sy1"><<</span> accumulate_future.<span class="me1">get</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
work_thread.<span class="me1">join</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// wait for thread completion</span>
<span class="br0">}</span></pre></div></div>
<p>Output:
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">result=21</pre></div></div>
</div>
<!--
NewPP limit report
Preprocessor visited node count: 5730/1000000
Preprocessor generated node count: 9322/1000000
Post‐expand include size: 177474/2097152 bytes
Template argument size: 35212/2097152 bytes
Highest expansion depth: 22/40
Expensive parser function count: 0/100
-->
<!-- Saved in parser cache with key mwiki1-mwiki_en_:pcache:idhash:2517-0!*!0!!en!*!* and timestamp 20151130143736 -->
</div> <!-- /bodycontent -->
<!-- printfooter -->
<div class="printfooter">
Retrieved from "<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/thread/promise&oldid=81978">http://en.cppreference.com/mwiki/index.php?title=cpp/thread/promise&oldid=81978</a>" </div>
<!-- /printfooter -->
<!-- catlinks -->
<div id='catlinks' class='catlinks catlinks-allhidden'></div> <!-- /catlinks -->
<div class="visualClear"></div>
<!-- debughtml -->
<!-- /debughtml -->
</div>
<!-- /bodyContent -->
</div>
</div>
<!-- /content -->
<!-- footer -->
<div id="cpp-footer-base" class="noprint">
<div id="footer">
<div id="cpp-navigation">
<h5>Navigation</h5>
<ul>
<li id="n-Support-us"><a href="http://www.cppreference.com/support" rel="nofollow">Support us</a></li><li id="n-recentchanges"><a href="http://en.cppreference.com/w/Special:RecentChanges" title="A list of recent changes in the wiki [r]" accesskey="r">Recent changes</a></li><li id="n-FAQ"><a href="http://en.cppreference.com/w/Cppreference:FAQ">FAQ</a></li><li id="n-Offline-version"><a href="http://en.cppreference.com/w/Cppreference:Archives">Offline version</a></li> </ul>
</div>
<div id="cpp-toolbox">
<h5><span>Toolbox</span><a href="promise.html#"></a></h5>
<ul>
<li id="t-whatlinkshere"><a href="http://en.cppreference.com/w/Special:WhatLinksHere/cpp/thread/promise" title="A list of all wiki pages that link here [j]" accesskey="j">What links here</a></li><li id="t-recentchangeslinked"><a href="http://en.cppreference.com/w/Special:RecentChangesLinked/cpp/thread/promise" title="Recent changes in pages linked from this page [k]" accesskey="k">Related changes</a></li><li id="t-upload"><a href="http://upload.cppreference.com/w/Special:Upload" title="Upload files [u]" accesskey="u">Upload file</a></li><li id="t-specialpages"><a href="http://en.cppreference.com/w/Special:SpecialPages" title="A list of all special pages [q]" accesskey="q">Special pages</a></li><li id="t-print"><a href="http://en.cppreference.com/mwiki/index.php?title=cpp/thread/promise&printable=yes" rel="alternate" title="Printable version of this page [p]" accesskey="p">Printable version</a></li><li id="t-permalink"><a href="http://en.cppreference.com/mwiki/index.php?title=cpp/thread/promise&oldid=81978" title="Permanent link to this revision of the page">Permanent link</a></li><li id="t-info"><a href="http://en.cppreference.com/mwiki/index.php?title=cpp/thread/promise&action=info">Page information</a></li> </ul>
</div>
<div id="cpp-languages">
<div><ul><li>In other languages</li></ul></div>
<div><ul>
<li class="interwiki-de"><a href="http://de.cppreference.com/w/cpp/thread/promise" title="cpp/thread/promise" lang="de" hreflang="de">Deutsch</a></li><li class="interwiki-es"><a href="http://es.cppreference.com/w/cpp/thread/promise" title="cpp/thread/promise" lang="es" hreflang="es">Español</a></li><li class="interwiki-fr"><a href="http://fr.cppreference.com/w/cpp/thread/promise" title="cpp/thread/promise" lang="fr" hreflang="fr">Français</a></li><li class="interwiki-it"><a href="http://it.cppreference.com/w/cpp/thread/promise" title="cpp/thread/promise" lang="it" hreflang="it">Italiano</a></li><li class="interwiki-ja"><a href="http://ja.cppreference.com/w/cpp/thread/promise" title="cpp/thread/promise" lang="ja" hreflang="ja">日本語</a></li><li class="interwiki-pt"><a href="http://pt.cppreference.com/w/cpp/thread/promise" title="cpp/thread/promise" lang="pt" hreflang="pt">Português</a></li><li class="interwiki-ru"><a href="http://ru.cppreference.com/w/cpp/thread/promise" title="cpp/thread/promise" lang="ru" hreflang="ru">Русский</a></li><li class="interwiki-zh"><a href="http://zh.cppreference.com/w/cpp/thread/promise" title="cpp/thread/promise" lang="zh" hreflang="zh">中文</a></li> </ul></div>
</div>
<ul id="footer-info">
<li id="footer-info-lastmod"> This page was last modified on 22 November 2015, at 18:10.</li>
<li id="footer-info-viewcount">This page has been accessed 67,829 times.</li>
</ul>
<ul id="footer-places">
<li id="footer-places-privacy"><a href="http://en.cppreference.com/w/Cppreference:Privacy_policy" title="Cppreference:Privacy policy">Privacy policy</a></li>
<li id="footer-places-about"><a href="http://en.cppreference.com/w/Cppreference:About" title="Cppreference:About">About cppreference.com</a></li>
<li id="footer-places-disclaimer"><a href="http://en.cppreference.com/w/Cppreference:General_disclaimer" title="Cppreference:General disclaimer">Disclaimers</a></li>
</ul>
<ul id="footer-icons" class="noprint">
<li id="footer-poweredbyico">
<a href="http://www.mediawiki.org/"><img src="../../../mwiki/skins/common/images/poweredby_mediawiki_88x31.png" alt="Powered by MediaWiki" width="88" height="31" /></a> <a href="http://qbnz.com/highlighter/"><img src="../../../../upload.cppreference.com/mwiki/images/2/2b/powered_by_geshi_88x31.png" alt="Powered by GeSHi" height="31" width="88" /></a> <a href="http://www.tigertech.net/referral/cppreference.com"><img src="../../../../upload.cppreference.com/mwiki/images/9/94/powered_by_tigertech_88x31.png" alt="Hosted by Tiger Technologies" height="31" width="88" /></a> </li>
</ul>
<div style="clear:both">
</div>
</div>
</div>
<!-- /footer -->
<script>if(window.mw){
mw.loader.state({"site":"loading","user":"missing","user.groups":"ready"});
}</script>
<script src="../../../mwiki/load.php%3Fdebug=false&lang=en&modules=skins.cppreference2&only=scripts&skin=cppreference2&*"></script>
<script>if(window.mw){
mw.loader.load(["mediawiki.action.view.postEdit","mediawiki.user","mediawiki.page.ready","mediawiki.searchSuggest","mediawiki.hidpi","ext.gadget.ColiruCompiler"], null, true);
}</script>
<script src="../../../mwiki/load.php%3Fdebug=false&lang=en&modules=site&only=scripts&skin=cppreference2&*"></script>
<script type="text/javascript">
var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www.");
document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E"));
</script>
<script type="text/javascript">
var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'UA-2828341-1']);
_gaq.push(['_setDomainName', 'cppreference.com']);
_gaq.push(['_trackPageview']);
</script><!-- Served in 2.041 secs. -->
</body>
<!-- Cached 20151130143742 -->
</html>
|
