-
Notifications
You must be signed in to change notification settings - Fork 1
Expand file tree
/
Copy pathfunction.html
More file actions
455 lines (389 loc) · 21.1 KB
/
function.html
File metadata and controls
455 lines (389 loc) · 21.1 KB
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
<!doctype html>
<html class="cpprefjp" lang="ja" itemscope="" itemtype="http://schema.org/WebPage">
<head>
<!-- Google tag (gtag.js) -->
<script async src="https://www.googletagmanager.com/gtag/js?id=G-NXNBNVBTJS"></script>
<script>
window.dataLayer = window.dataLayer || [];
function gtag(){dataLayer.push(arguments);}
gtag('js', new Date());
gtag('config', 'G-NXNBNVBTJS');
</script>
<meta charset="UTF-8">
<title>function - cpprefjp C++日本語リファレンス</title>
<meta name="viewport" content="width=device-width,initial-scale=1">
<meta name="keywords" content="
C++,標準ライブラリ,リファレンス,ドキュメント,STL,std,functional,std,class template,cpp11
">
<meta name="title" content="function - cpprefjp C++日本語リファレンス" />
<meta itemprop="name" content="function - cpprefjp C++日本語リファレンス" />
<meta property="og:title" content="function - cpprefjp C++日本語リファレンス" />
<meta property="og:url" content="https://cpprefjp.github.io/reference/functional/function.html" />
<meta property="og:site_name" content="cpprefjp - C++日本語リファレンス" />
<meta property="og:type" content="article" />
<meta property="og:description" content="`function`クラステンプレートは、パラメータの型リスト`ArgTypes...`、戻り値の型`R`に合致する、あらゆる関数ポインタ、関数オブジェクト、メンバ関数ポインタ、メンバ変数ポインタを保持できるクラスである。" />
<meta name="twitter:card" content="summary" />
<meta name="twitter:title" content="function - cpprefjp C++日本語リファレンス" />
<meta name="twitter:url" content="https://cpprefjp.github.io/reference/functional/function.html" />
<meta name="twitter:description" content="`function`クラステンプレートは、パラメータの型リスト`ArgTypes...`、戻り値の型`R`に合致する、あらゆる関数ポインタ、関数オブジェクト、メンバ関数ポインタ、メンバ変数ポインタを保持できるクラスである。" />
<link rel="alternate" type="application/atom+xml" title="Atom" href="https://cpprefjp.github.io/rss.xml" />
<link rel="apple-touch-icon" sizes="180x180" href="../../static/favicons/apple-touch-icon.png?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95">
<link rel="icon" type="image/png" sizes="32x32" href="../../static/favicons/favicon-32x32.png?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95">
<link rel="icon" type="image/png" sizes="16x16" href="../../static/favicons/favicon-16x16.png?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95">
<link rel="manifest" href="../../manifest.json?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95">
<meta name="theme-color" content="#f5f8fc">
<link rel="stylesheet" href="../../static/pygments/default.css?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95">
<!-- <link rel="stylesheet" href="../../static/css/root.css"> -->
<link href="../../static/kunai/css/kunai-stage-0.css?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95" rel="stylesheet">
<link href="../../static/kunai/css/kunai-stage-1.css?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95" rel="stylesheet">
<link href="../../static/kunai/css/kunai-stage-2.css?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95" rel="stylesheet">
<link href="../../static/kunai/css/kunai-stage-3.css?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95" rel="stylesheet">
<script type="text/javascript" src="../../static/kunai/js/kunai-vendor.js?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95"></script>
<script type="text/javascript" src="../../static/kunai/js/kunai.js?cachebust=be86fa2321ebe02b6955b61b98b778e377bcbf95"></script>
<script type="text/javascript">
document.addEventListener('DOMContentLoaded', function() {
var kn = new Kunai;
kn.cpprefjp();
});
</script>
</head>
<body>
<header data-kunai-mdinfo="{"meta": {"header": ["functional"], "namespace": ["std"], "id-type": ["class template"], "cpp": ["cpp11"]}, "sources": [{"id": "20acec2586927979ee8b7aa52afeb940acd25b1b", "source": "#include <iostream>\n#include <functional>\n\nint add(int x) { return x + 1; }\n\nint main()\n{\n // \u95a2\u6570\u3092\u4ee3\u5165\n std::function<int(int)> f = add;\n\n // \u95a2\u6570\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u4ee3\u5165\n f = [](int x) { return x + 1; };\n\n // \u4fdd\u6301\u3057\u3066\u3044\u308b\u95a2\u6570\u3092\u547c\u3073\u51fa\u3059\n int result = f(1);\n std::cout << result << std::endl;\n}\n"}], "page_id": ["reference", "functional", "function"]}">
<nav class="navbar navbar-default" role="navigation">
<div class="container-fluid">
<div class="navbar-header">
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar-collapse">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand" href="../../index.html">
<div class="title-wrapper clearfix">
<div class="title">cpprefjp - C++日本語リファレンス</div>
</div>
</a>
</div>
<div class="collapse navbar-collapse" id="navbar-collapse">
<ul class="nav navbar-nav navbar-right">
<li>
<div class="google-search">
<script>
(function() {
var cx = '013316413321391058734:ji_u66hl7hq';
var gcse = document.createElement('script');
gcse.type = 'text/javascript';
gcse.async = true;
gcse.src = (document.location.protocol == 'https:' ? 'https:' : 'http:') +
'//www.google.com/cse/cse.js?cx=' + cx;
var s = document.getElementsByTagName('script')[0];
s.parentNode.insertBefore(gcse, s);
})();
</script>
<div class="gcse-search"></div>
</div>
</li>
<li>
<a href="https://github.com/cpprefjp/site">GitHub Project</a>
</li>
</ul>
</div>
</div>
</nav>
</header>
<main id="main" role="main">
<div class="container-fluid">
<div class="row">
<div class="col-sm-9 col-sm-push-3" itemscope itemtype="http://schema.org/Article">
<div class="row">
<div class="col-sm-12 google-search-result">
<gcse:searchresults></gcse:searchresults>
</div>
</div>
<div class="row">
<div class="col-sm-12 content-header">
<ol class="breadcrumb">
<li itemscope itemtype="http://www.schema.org/SiteNavigationElement">
<span>
<a href="../../index.html" itemprop="url">
<i class="fa fa-fw fa-home"></i>
</a>
</span>
</li>
<li itemscope itemtype="http://www.schema.org/SiteNavigationElement">
<span>
<a href="../../reference.html" itemprop="url">
<span itemprop="name">リファレンス</span>
</a>
</span>
</li>
<li itemscope itemtype="http://www.schema.org/SiteNavigationElement">
<span>
<a href="../../reference/functional.html" itemprop="url">
<span itemprop="name">functional</span>
</a>
</span>
</li>
<li class="active" itemscope itemtype="http://www.schema.org/SiteNavigationElement">
<span>
<span itemprop="name">function</span>
</span>
</li>
</ol>
<div class="crsearch"></div>
</div>
</div>
<div class="row">
<div class="col-sm-12 edit-button">
<p class="text-right"><small>
最終更新日時(UTC):
<span itemprop="datePublished" content="2025-09-10T05:09:23">
2025年09月10日 05時09分23秒
</span>
<br/>
<span itemprop="author" itemscope itemtype="http://schema.org/Person">
<span itemprop="name">Akira Takahashi</span>
</span>
が更新
</small></p>
<p class="text-right">
<a class="history" target="_blank" href="https://github.com/cpprefjp/site/commits/master/reference/functional/function.md">
<span class="fa fa-fw fa-clock-o fa-flip-horizontal"></span>履歴
</a>
<a class="edit" target="_blank" href="https://github.com/cpprefjp/site/edit/master/reference/functional/function.md">
<span class="fa fa-fw fa-pencil"></span>編集
</a>
</p>
</div>
</div>
<div class="row">
<div class="col-sm-12 content-body">
<div class="identifier-type">class template</div><div class="header"><functional></div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="token">function</span><span class="cpp cpp11" title="C++11で追加">(C++11)</span></h1>
<div itemprop="articleBody"><p><div class="codehilite"><pre><span></span><code><span class="k">namespace</span><span class="w"> </span><span class="nn">std</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="o">></span><span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">function</span><span class="p">;</span><span class="w"> </span><span class="c1">// 宣言のみ</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">R</span><span class="p">,</span><span class="w"> </span><span class="k">class</span><span class="p">...</span><span class="w"> </span><span class="n">ArgTypes</span><span class="o">></span>
<span class="w"> </span><span class="k">class</span><span class="w"> </span><span class="nc">function</span><span class="o"><</span><span class="n">R</span><span class="p">(</span><span class="n">ArgTypes</span><span class="p">...)</span><span class="o">></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
</p>
<h2>概要</h2>
<p><code>function</code>クラステンプレートは、パラメータの型リスト<code>ArgTypes...</code>、<a class="cpprefjp-defined-word" data-desc="関数呼び出し式の評価結果となるオブジェクト・値">戻り値</a>の型<code>R</code>に合致する、あらゆる関数ポインタ、関数オブジェクト、メンバ関数ポインタ、メンバ変数ポインタを保持できるクラスである。</p>
<p>このクラスは、以下のように使用する：</p>
<p><div class="codehilite"><pre><span></span><code><span class="kt">int</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="p">}</span>
<span class="c1">// 関数を変数に保持する</span>
<span class="n">function</span><span class="o"><</span><span class="kt">int</span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="o">></span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">add</span><span class="p">;</span>
<span class="c1">// 保持している関数を呼び出す</span>
<span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">f</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span><span class="w"> </span><span class="c1">// result == 2</span>
</code></pre></div>
</p>
<p><code>function</code>のテンプレート引数には、「<a class="cpprefjp-defined-word" data-desc="関数呼び出し式の評価結果となるオブジェクト・値">戻り値</a>の型(引数の型リスト...)」という形式で、型で関数のシグニチャを指定する。</p>
<p><code>function</code>クラスは具体的な関数・関数オブジェクトの型には依存しない。シグニチャが一致していればあらゆる型の関数、関数オブジェクトを代入できる。</p>
<h2>備考</h2>
<ul>
<li><code>function<int(int arg1, double arg2)></code>のように、パラメータに名前を付けることもできるが、名前は単に無視される</li>
</ul>
<h2>メンバ関数</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<thead>
<tr>
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
</tr>
</thead>
<tbody>
<tr>
<td><code><a href="function/op_constructor.html">(constructor)</a></code></td>
<td>コンストラクタ</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="function/op_destructor.html">(destructor)</a></code></td>
<td>デストラクタ</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="function/op_assign.html">operator=</a></code></td>
<td>代入演算子</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="function/swap.html">swap</a></code></td>
<td>他の<code>function</code>オブジェクトと中身を入れ替える</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="function/assign.html">assign</a></code></td>
<td>関数オブジェクトとアロケータを再代入する</td>
<td>C++11<br /> C++17で削除</td>
</tr>
<tr>
<td><code><a href="function/op_bool.html">operator bool</a></code></td>
<td>関数呼び出しが可能か調べる</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="function/op_call.html">operator()</a></code></td>
<td>関数呼び出し</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="function/target_type.html">target_type</a></code></td>
<td>元となる関数の型情報を取得する</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="function/target.html">target</a></code></td>
<td>元となる関数を取得する</td>
<td>C++11</td>
</tr>
</tbody>
</table>
<h2>メンバ型</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<thead>
<tr>
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>result_type</code></td>
<td>関数の<a class="cpprefjp-defined-word" data-desc="関数呼び出し式の評価結果となるオブジェクト・値">戻り値</a>の型(テンプレートパラメータ<code>R</code>)</td>
<td>C++11</td>
</tr>
<tr>
<td><code>argument_type</code></td>
<td>第1引数の型(引数が1つの場合のみ定義される)</td>
<td>C++11<br /> C++17から非推奨<br /> C++20で削除</td>
</tr>
<tr>
<td><code>first_argument_type</code></td>
<td>第1引数の型(引数が2つの場合のみ定義される)</td>
<td>C++11<br /> C++17から非推奨<br /> C++20で削除</td>
</tr>
<tr>
<td><code>second_argument_type</code></td>
<td>第2引数の型(引数が2つの場合のみ定義される)</td>
<td>C++11<br /> C++17から非推奨<br /> C++20で削除</td>
</tr>
</tbody>
</table>
<h2>非メンバ関数</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<thead>
<tr>
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
</tr>
</thead>
<tbody>
<tr>
<td><code><a href="function/op_equal.html">operator==</a></code></td>
<td>等値比較</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="function/op_not_equal.html">operator!=</a></code></td>
<td>非等値比較</td>
<td>C++11</td>
</tr>
<tr>
<td><code><a href="function/swap_free.html">swap</a></code></td>
<td>2つの<code>function</code>オブジェクトを入れ替える</td>
<td>C++11</td>
</tr>
</tbody>
</table>
<h2>推論補助</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<thead>
<tr>
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
</tr>
</thead>
<tbody>
<tr>
<td><code><a href="function/op_deduction_guide.html">(deduction_guide)</a></code></td>
<td>クラステンプレートの推論補助</td>
<td>C++17</td>
</tr>
</tbody>
</table>
<h2>その他</h2>
<table border="1" bordercolor="#888" style="border-collapse:collapse">
<thead>
<tr>
<th>名前</th>
<th>説明</th>
<th>対応バージョン</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>uses_allocator</code></td>
<td><code>function</code>による特殊化</td>
<td>C++11<br /> C++17で削除</td>
</tr>
</tbody>
</table>
<h2>例</h2>
<p><div class="yata" id="20acec2586927979ee8b7aa52afeb940acd25b1b"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../iostream.html"><iostream></a></span>
<span class="cp">#include <a href="../functional.html"><functional></a></span>
<span class="kt">int</span><span class="w"> </span><span class="nf">add</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="p">}</span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="w"> </span><span class="c1">// 関数を代入</span>
<span class="w"> </span><span class="n"><span style="color:#ff0000">std::function</span></span><span class="o"><</span><span class="kt">int</span><span class="p">(</span><span class="kt">int</span><span class="p">)</span><span class="o">></span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">add</span><span class="p">;</span>
<span class="w"> </span><span class="c1">// 関数オブジェクトを代入</span>
<span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">[](</span><span class="kt">int</span><span class="w"> </span><span class="n">x</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="p">};</span>
<span class="w"> </span><span class="c1">// 保持している関数を呼び出す</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="function/op_call.html">f(1)</a></span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">result</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h3>出力</h3>
<p><pre><code>2
</code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<ul>
<li>C++11</li>
</ul>
<h2>関連項目</h2>
<ul>
<li>C++23 <code><a href="move_only_function.html">move_only_function</a></code></li>
<li>C++26 <code><a href="copyable_function.html">copyable_function</a></code></li>
<li>C++26 <code><a href="function_ref.html">function_ref</a></code></li>
</ul>
<h2>参照</h2>
<ul>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0302r1.html" target="_blank">P0302R1 Removing Allocator Support in <code>std::function</code> (rev 1)</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0005r4.html" target="_blank">P0005R4 Adopt <code>not_fn</code> from Library Fundamentals 2 for C++17</a></li>
<li><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0619r4.html" target="_blank">P0619R4 Reviewing deprecated facilities of C++17 for C++20</a></li>
</ul></div>
</div>
</div>
</div>
<div id="sidebar" class="col-sm-3 col-sm-pull-9">
</div>
</div>
</div>
</main>
<footer class="footer navbar navbar-default">
<div class="container-fluid">
<p><small>
本サイトの情報は、
<a href="https://creativecommons.org/licenses/by/4.0/deed.ja" rel="nofollow">クリエイティブ・コモンズ 表示 4.0 非移植 ライセンス(CC BY)</a>
の下に提供されています。
</small></p>
</div>
</footer>
</body>
</html>