{"id":5536,"date":"2021-09-10T17:01:47","date_gmt":"2021-09-10T09:01:47","guid":{"rendered":"https:\/\/damogame.cn:15443\/wordpress\/?p=5536"},"modified":"2021-09-10T17:01:47","modified_gmt":"2021-09-10T09:01:47","slug":"c11%e6%a8%a1%e7%89%88%e5%85%83%e7%bc%96%e7%a8%8b","status":"publish","type":"post","link":"https:\/\/i007.cc\/wordpress\/archives\/5536","title":{"rendered":"C++11\u6a21\u7248\u5143\u7f16\u7a0b"},"content":{"rendered":"<p><a href=\"https:\/\/www.cnblogs.com\/qicosmos\/p\/4480460.html\">\u539f\u6587\u5730\u5740<\/a><\/p>\n<p>&nbsp;<\/p>\n<div class=\"postbody\">\n<div id=\"cnblogs_post_body\" class=\"blogpost-body blogpost-body-html\">\n<h3>1.\u6982\u8ff0<\/h3>\n<p>\u6a21\u7248\u5143\u7f16\u7a0b\uff08template metaprogram\uff09\u662fC++\u4e2d\u6700\u590d\u6742\u4e5f\u662f\u5a01\u529b\u6700\u5f3a\u5927\u7684\u7f16\u7a0b\u8303\u5f0f\uff0c\u5b83\u662f\u4e00\u79cd\u53ef\u4ee5\u521b\u5efa\u548c\u64cd\u7eb5\u7a0b\u5e8f\u7684\u7a0b\u5e8f\u3002\u6a21\u7248\u5143\u7f16\u7a0b\u5b8c\u5168\u4e0d\u540c\u4e8e\u666e\u901a\u7684\u8fd0\u884c\u671f\u7a0b\u5e8f\uff0c\u5b83\u5f88\u72ec\u7279\uff0c\u56e0\u4e3a\u6a21\u7248\u5143\u7a0b\u5e8f\u7684\u6267\u884c\u5b8c\u5168\u662f\u5728\u7f16\u8bd1\u671f\uff0c\u5e76\u4e14\u6a21\u7248\u5143\u7a0b\u5e8f\u64cd\u7eb5\u7684\u6570\u636e\u4e0d\u80fd\u662f\u8fd0\u884c\u65f6\u53d8\u91cf\uff0c\u53ea\u80fd\u662f\u7f16\u8bd1\u671f\u5e38\u91cf\uff0c\u4e0d\u53ef\u4fee\u6539\uff0c\u53e6\u5916\u5b83\u7528\u5230\u7684\u8bed\u6cd5\u5143\u7d20\u4e5f\u662f\u76f8\u5f53\u6709\u9650\uff0c\u4e0d\u80fd\u4f7f\u7528\u8fd0\u884c\u671f\u7684\u4e00\u4e9b\u8bed\u6cd5\uff0c\u6bd4\u5982if-else\uff0cfor\u7b49\u8bed\u53e5\u90fd\u4e0d\u80fd\u7528\u3002\u56e0\u6b64\uff0c\u6a21\u7248\u5143\u7f16\u7a0b\u9700\u8981\u5f88\u591a\u6280\u5de7\uff0c\u5e38\u5e38\u9700\u8981\u7c7b\u578b\u91cd\u5b9a\u4e49\u3001\u679a\u4e3e\u5e38\u91cf\u3001\u7ee7\u627f\u3001\u6a21\u677f\u504f\u7279\u5316\u7b49\u65b9\u6cd5\u6765\u914d\u5408\uff0c\u56e0\u6b64\u7f16\u5199\u6a21\u7248\u5143\u7f16\u7a0b\u6bd4\u8f83\u590d\u6742\u4e5f\u6bd4\u8f83\u56f0\u96be\u3002<\/p>\n<p>\u73b0\u5728C++11\u65b0\u589e\u4e86\u4e00\u4e9b\u6a21\u7248\u5143\u76f8\u5173\u7684\u7279\u6027\uff0c\u4e0d\u4ec5\u53ef\u4ee5\u8ba9\u6211\u4eec\u7f16\u5199\u6a21\u7248\u5143\u7a0b\u5e8f\u53d8\u5f97\u66f4\u5bb9\u6613\uff0c\u8fd8\u8fdb\u4e00\u6b65\u589e\u5f3a\u4e86\u6cdb\u578b\u7f16\u7a0b\u7684\u80fd\u529b\uff0c\u6bd4\u5982type_traits\u8ba9\u6211\u4eec\u4e0d\u5fc5\u518d\u91cd\u590d\u53d1\u660e\u8f6e\u5b50\u4e86\uff0c\u7ed9\u6211\u4eec\u63d0\u4f9b\u4e86\u5927\u91cf\u4fbf\u5229\u7684\u5143\u51fd\u6570\uff0c\u8fd8\u63d0\u4f9b\u4e86\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u548ctuple\uff0c\u8ba9\u6a21\u7248\u5143\u7f16\u7a0b\u201c\u5982\u864e\u6dfb\u7ffc\u201d\u3002\u672c\u6587\u5c06\u5411\u8bfb\u8005\u5c55\u793aC++11\u4e2d\u6a21\u7248\u5143\u7f16\u7a0b\u5e38\u7528\u7684\u6280\u5de7\u548c\u5177\u4f53\u5e94\u7528\u3002<\/p>\n<h3>2.\u6a21\u7248\u5143\u57fa\u672c\u6982\u5ff5<\/h3>\n<p>\u6a21\u7248\u5143\u7a0b\u5e8f\u7531\u5143\u6570\u636e\u548c\u5143\u51fd\u6570\u7ec4\u6210\uff0c\u5143\u6570\u636e\u5c31\u662f\u5143\u7f16\u7a0b\u53ef\u4ee5\u64cd\u4f5c\u7684\u6570\u636e\uff0c\u5373C++\u7f16\u8bd1\u5668\u5728\u7f16\u8bd1\u671f\u53ef\u4ee5\u64cd\u4f5c\u7684\u6570\u636e\u3002\u5143\u6570\u636e\u4e0d\u662f\u8fd0\u884c\u671f\u53d8\u91cf\uff0c\u53ea\u80fd\u662f\u7f16\u8bd1\u671f\u5e38\u91cf\uff0c\u4e0d\u80fd\u4fee\u6539\uff0c\u5e38\u89c1\u7684\u5143\u6570\u636e\u6709enum\u679a\u4e3e\u5e38\u91cf\u3001\u9759\u6001\u5e38\u91cf\u3001\u57fa\u672c\u7c7b\u578b\u548c\u81ea\u5b9a\u4e49\u7c7b\u578b\u7b49\u3002<\/p>\n<p>\u5143\u51fd\u6570\u662f\u6a21\u677f\u5143\u7f16\u7a0b\u4e2d\u7528\u4e8e\u64cd\u4f5c\u5904\u7406\u5143\u6570\u636e\u7684\u201c\u6784\u4ef6\u201d\uff0c\u53ef\u4ee5\u5728\u7f16\u8bd1\u671f\u88ab\u201c\u8c03\u7528\u201d\uff0c\u56e0\u4e3a\u5b83\u7684\u529f\u80fd\u548c\u5f62\u5f0f\u548c\u8fd0\u884c\u65f6\u7684\u51fd\u6570\u7c7b\u4f3c\uff0c\u800c\u88ab\u79f0\u4e3a\u5143\u51fd\u6570\uff0c\u5b83\u662f\u5143\u7f16\u7a0b\u4e2d\u6700\u91cd\u8981\u7684\u6784\u4ef6\u3002\u5143\u51fd\u6570\u5b9e\u9645\u4e0a\u8868\u73b0\u4e3aC++\u7684\u4e00\u4e2a\u7c7b\u3001\u6a21\u677f\u7c7b\u6216\u6a21\u677f\u51fd\u6570\uff0c\u5b83\u7684\u901a\u5e38\u5f62\u5f0f\u5982\u4e0b\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<pre>template&lt;int N, int M&gt;\r\nstruct meta_func\r\n{\r\n    static const int value = N+M;\r\n}<\/pre>\n<\/div>\n<p>\u8c03\u7528\u5143\u51fd\u6570\u83b7\u53d6value\u503c\uff1acout&lt;&lt;meta_func&lt;1, 2&gt;::value&lt;&lt;endl;<\/p>\n<p>meta_func\u7684\u6267\u884c\u8fc7\u7a0b\u662f\u5728\u7f16\u8bd1\u671f\u5b8c\u6210\u7684\uff0c\u5b9e\u9645\u6267\u884c\u7a0b\u5e8f\u65f6\uff0c\u662f\u6ca1\u6709\u8ba1\u7b97\u52a8\u4f5c\u800c\u662f\u76f4\u63a5\u4f7f\u7528\u7f16\u8bd1\u671f\u7684\u8ba1\u7b97\u7ed3\u679c\u7684\u3002\u5143\u51fd\u6570\u53ea\u5904\u7406\u5143\u6570\u636e\uff0c\u5143\u6570\u636e\u662f\u7f16\u8bd1\u671f\u5e38\u91cf\u548c\u7c7b\u578b\uff0c\u6240\u4ee5\u4e0b\u9762\u7684\u4ee3\u7801\u662f\u7f16\u8bd1\u4e0d\u8fc7\u7684\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<pre>int i = 1, j = 2;\r\nmeta_func&lt;i, j&gt;::value; \/\/\u9519\u8bef\uff0c\u5143\u51fd\u6570\u65e0\u6cd5\u5904\u7406\u8fd0\u884c\u65f6\u666e\u901a\u6570\u636e<\/pre>\n<\/div>\n<p>\u6a21\u677f\u5143\u7f16\u7a0b\u4ea7\u751f\u7684\u6e90\u7a0b\u5e8f\u662f\u5728\u7f16\u8bd1\u671f\u6267\u884c\u7684\u7a0b\u5e8f\uff0c\u56e0\u6b64\u5b83\u9996\u5148\u8981\u9075\u5faaC++\u548c\u6a21\u677f\u7684\u8bed\u6cd5\uff0c\u4f46\u662f\u5b83\u64cd\u4f5c\u7684\u5bf9\u8c61\u4e0d\u662f\u8fd0\u884c\u65f6\u666e\u901a\u7684\u53d8\u91cf\uff0c\u56e0\u6b64\u4e0d\u80fd\u4f7f\u7528\u8fd0\u884c\u65f6\u7684C++\u5173\u952e\u5b57\uff08\u5982if\u3001else\u3001for\uff09\uff0c\u53ef\u7528\u7684\u8bed\u6cd5\u5143\u7d20\u76f8\u5f53\u6709\u9650\uff0c\u6700\u5e38\u7528\u7684\u662f\uff1a<\/p>\n<ul>\n<li>enum\u3001static const\uff0c\u7528\u6765\u5b9a\u4e49\u7f16\u8bd1\u671f\u7684\u6574\u6570\u5e38\u91cf\uff1b<\/li>\n<li>typedef\/using\uff0c\u7528\u4e8e\u5b9a\u4e49\u5143\u6570\u636e\uff1b<\/li>\n<li>T\u3001Args&#8230;\uff0c\u58f0\u660e\u5143\u6570\u636e\u7c7b\u578b\uff1b<\/li>\n<li>template\uff0c\u4e3b\u8981\u7528\u4e8e\u5b9a\u4e49\u5143\u51fd\u6570\uff1b<\/li>\n<li>&#8220;::&#8221;\uff0c\u57df\u8fd0\u7b97\u7b26\uff0c\u7528\u4e8e\u89e3\u6790\u7c7b\u578b\u4f5c\u7528\u57df\u83b7\u53d6\u8ba1\u7b97\u7ed3\u679c\uff08\u5143\u6570\u636e\uff09\u3002<\/li>\n<\/ul>\n<p>\u5982\u679c\u6a21\u677f\u5143\u7f16\u7a0b\u4e2d\u9700\u8981if-else\u3001for\u7b49\u903b\u8f91\u65f6\u8be5\u600e\u4e48\u529e\u5462\uff1f<\/p>\n<p align=\"left\">\u6a21\u677f\u5143\u4e2d\u7684if-else\u53ef\u4ee5\u901a\u8fc7type_traits\u6765\u5b9e\u73b0\uff0c\u5b83\u4e0d\u4ec5\u4ec5\u53ef\u4ee5\u5728\u7f16\u8bd1\u671f\u505a\u5224\u65ad\uff0c\u8fd8\u53ef\u4ee5\u505a\u8ba1\u7b97\u3001\u67e5\u8be2\u3001\u8f6c\u6362\u548c\u9009\u62e9\u3002<\/p>\n<p align=\"left\">\u6a21\u677f\u5143\u4e2d\u7684for\u7b49\u903b\u8f91\u53ef\u4ee5\u901a\u8fc7\u9012\u5f52\u3001\u91cd\u8f7d\u3001\u548c\u6a21\u677f\u7279\u5316\uff08\u504f\u7279\u5316\uff09\u7b49\u65b9\u6cd5\u5b9e\u73b0\u3002<\/p>\n<p align=\"left\">\u4e0b\u9762\u6765\u770b\u770bC++11\u63d0\u4f9b\u7684\u6a21\u7248\u5143\u57fa\u7840\u5e93type_traits\u3002<\/p>\n<h3>3.type_traits<\/h3>\n<p>type_traits\u662fC++11\u63d0\u4f9b\u7684\u6a21\u677f\u5143\u57fa\u7840\u5e93\uff0c\u901a\u8fc7type_traits\u53ef\u4ee5\u5b9e\u73b0\u5728\u7f16\u8bd1\u671f\u8ba1\u7b97\u3001\u67e5\u8be2\u3001\u5224\u65ad\u3001\u8f6c\u6362\u548c\u9009\u62e9\uff0c\u63d0\u4f9b\u4e86\u6a21\u677f\u5143\u7f16\u7a0b\u9700\u8981\u7684\u4e00\u4e9b\u5e38\u7528\u5143\u51fd\u6570\u3002\u4e0b\u9762\u6765\u770b\u770b\u4e00\u4e9b\u57fa\u672c\u7684type_traits\u7684\u57fa\u672c\u7528\u6cd5\u3002<\/p>\n<p>\u6700\u7b80\u5355\u7684\u4e00\u4e2atype_traits\u662f\u5b9a\u4e49\u7f16\u8bd1\u671f\u5e38\u91cf\u7684\u5143\u51fd\u6570integral_constant\uff0c\u5b83\u7684\u5b9a\u4e49\u5982\u4e0b\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<pre>template&lt; class T, T v &gt;\r\nstruct integral_constant;<\/pre>\n<\/div>\n<p>\u501f\u52a9\u8fd9\u4e2a\u7b80\u5355\u7684trait\uff0c\u6211\u4eec\u53ef\u4ee5\u5f88\u65b9\u4fbf\u5730\u5b9a\u4e49\u7f16\u8bd1\u671f\u5e38\u91cf\uff0c\u6bd4\u5982\u5b9a\u4e49\u4e00\u4e2a\u503c\u4e3a1\u7684int\u5e38\u91cf\u53ef\u4ee5\u8fd9\u6837\u5b9a\u4e49\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<pre>using one_type = std::integral_constant&lt;int, 1&gt;;<\/pre>\n<\/div>\n<p>\u6216\u8005<\/p>\n<div class=\"cnblogs_code\">\n<pre>template&lt;class T&gt;\r\nstruct one_type : std::integral_constant&lt;int, 1&gt;{};<\/pre>\n<\/div>\n<p>\u83b7\u53d6\u5e38\u91cf\u5219\u901a\u8fc7one_type::value\u6765\u83b7\u53d6\uff0c\u8fd9\u79cd\u5b9a\u4e49\u7f16\u8bd1\u671f\u5e38\u91cf\u7684\u65b9\u5f0f\u76f8\u6bd4C++98\/03\u8981\u7b80\u5355\uff0c\u5728C++98\/03\u4e2d\u5b9a\u4e49\u7f16\u8bd1\u671f\u5e38\u91cf\u4e00\u822c\u662f\u8fd9\u6837\u5b9a\u4e49\u7684\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>template&lt;class T&gt;\r\nstruct one_type\r\n{\r\n    enum{value = 1};\r\n};\r\n\r\ntemplate&lt;class T&gt;\r\nstruct one_type\r\n{\r\n    static const int value = 1;\r\n};<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>\u53ef\u4ee5\u770b\u5230\uff0c\u901a\u8fc7C++11\u7684type_traits\u63d0\u4f9b\u7684\u4e00\u4e2a\u7b80\u5355\u7684integral_constant\u5c31\u53ef\u4ee5\u5f88\u65b9\u4fbf\u7684\u5b9a\u4e49\u7f16\u8bd1\u671f\u5e38\u91cf\uff0c\u800c\u65e0\u9700\u518d\u53bb\u901a\u8fc7\u5b9a\u4e49enum\u548cstatic const\u53d8\u91cf\u65b9\u5f0f\u53bb\u5b9a\u4e49\u7f16\u8bd1\u671f\u5e38\u91cf\u4e86\uff0c\u8fd9\u4e5f\u4e3a\u5b9a\u4e49\u7f16\u8bd1\u671f\u5e38\u91cf\u63d0\u4f9b\u4e86\u53e6\u5916\u4e00\u79cd\u65b9\u6cd5\u3002C++11\u7684type_traits\u5df2\u7ecf\u63d0\u4f9b\u4e86\u7f16\u8bd1\u671f\u7684true\u548cfalse\uff0c\u662f\u901a\u8fc7integral_constant\u6765\u5b9a\u4e49\u7684\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<pre>typedef  integral_constant&lt;bool, true&gt; true_type;\r\ntypedef  integral_constant&lt;bool, false&gt; false_type;<\/pre>\n<\/div>\n<p>\u9664\u4e86\u8fd9\u4e9b\u57fa\u672c\u7684\u5143\u51fd\u6570\u4e4b\u5916\uff0ctype_traits\u8fd8\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u5143\u51fd\u6570\uff0c\u6bd4\u5982\u7528\u4e8e\u7f16\u8bd1\u671f\u5224\u65ad\u7684\u5143\u51fd\u6570\uff1a<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"medium-zoom-image\" src=\"https:\/\/images0.cnblogs.com\/blog2015\/468725\/201505\/052127020957357.png\" alt=\"\" width=\"721\" height=\"482\" \/><\/p>\n<p>\u8fd9\u53ea\u662f\u5217\u4e3e\u4e00\u5c0f\u90e8\u5206\u7684type_traits\u5143\u51fd\u6570\uff0ctype_traits\u63d0\u4f9b\u4e86\u4e0a\u767e\u4e2a\u65b9\u4fbf\u7684\u5143\u51fd\u6570\uff0c\u8bfb\u8005\u53ef\u4ee5\u53c2\u8003http:\/\/en.cppreference.com\/w\/cpp\/header\/type_traits\uff0c\u8fd9\u4e9b\u57fa\u672c\u7684\u5143\u51fd\u6570\u7528\u6cd5\u6bd4\u8f83\u7b80\u5355\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>#include &lt;iostream&gt;\r\n#include &lt;type_traits&gt;\r\n\r\nint main() {\r\n  std::cout &lt;&lt; \"int: \" &lt;&lt; std::is_const&lt;int&gt;::value &lt;&lt; std::endl;\r\n  std::cout &lt;&lt; \"const int: \" &lt;&lt; std::is_const&lt;const int&gt;::value &lt;&lt; std::endl;\r\n\r\n  \/\/\u5224\u65ad\u7c7b\u578b\u662f\u5426\u76f8\u540c\r\n  std::cout&lt;&lt; std::is_same&lt;int, int&gt;::value&lt;&lt;\"\\n\";\/\/ true\r\n  std::cout&lt;&lt; std::is_same&lt;int, unsignedint&gt;::value&lt;&lt;\"\\n\";\/\/ false\r\n\r\n  \/\/\u6dfb\u52a0\u3001\u79fb\u9664const\r\n  cout &lt;&lt; std::is_same&lt;const int, add_const&lt;int&gt;::type&gt;::value &lt;&lt; endl;\r\n  cout &lt;&lt; std::is_same&lt;int, remove_const&lt;const int&gt;::type&gt;::value &lt;&lt; endl;\r\n\r\n  \/\/\u6dfb\u52a0\u5f15\u7528\r\n  cout &lt;&lt; std::is_same&lt;int&amp;, add_lvalue_reference&lt;int&gt;::type&gt;::value &lt;&lt; endl;\r\n  cout &lt;&lt; std::is_same&lt;int&amp;&amp;, add_rvalue_reference&lt;int&gt;::type&gt;::value &lt;&lt; endl;\r\n\r\n  \/\/\u53d6\u516c\u5171\u7c7b\u578b\r\n  typedef std::common_type&lt;unsigned char, short, int&gt;::type NumericType;\r\n  cout &lt;&lt; std::is_same&lt;int, NumericType&gt;::value &lt;&lt; endl;\r\n\r\n  return 0;\r\n}<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>type_traits\u8fd8\u63d0\u4f9b\u4e86\u7f16\u8bd1\u671f\u9009\u62e9traits\uff1astd::conditional\uff0c\u5b83\u5728\u7f16\u8bd1\u671f\u6839\u636e\u4e00\u4e2a\u5224\u65ad\u5f0f\u9009\u62e9\u4e24\u4e2a\u7c7b\u578b\u4e2d\u7684\u4e00\u4e2a\uff0c\u548c\u6761\u4ef6\u8868\u8fbe\u5f0f\u7684\u8bed\u4e49\u7c7b\u4f3c\uff0c\u7c7b\u4f3c\u4e8e\u4e00\u4e2a\u4e09\u5143\u8868\u8fbe\u5f0f\u3002\u5b83\u7684\u539f\u578b\u662f\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<pre>template&lt; bool B, class T, class F &gt;\r\nstruct conditional;<\/pre>\n<\/div>\n<p>\u7528\u6cd5\u6bd4\u8f83\u7b80\u5355\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>#include &lt;iostream&gt;\r\n#include &lt;type_traits&gt;\r\n\r\nint main() \r\n{\r\n    typedef std::conditional&lt;true,int,float&gt;::type A;               \/\/ int\r\n    typedef std::conditional&lt;false,int,float&gt;::type B;              \/\/ float\r\n\r\n    typedef std::conditional&lt;(sizeof(long long) &gt;sizeof(long double)),\r\n    long long, long double&gt;::type max_size_t;\r\n\r\n    cout&lt;&lt;typeid(max_size_t).name()&lt;&lt;endl;  \/\/long double\r\n}<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>\u53e6\u5916\u4e00\u4e2a\u5e38\u7528\u7684type_traits\u662fstd::decay(\u673d\u5316)\uff0c\u5b83\u5bf9\u4e8e\u666e\u901a\u7c7b\u578b\u6765\u8bf4std::decay\uff08\u673d\u5316\uff09\u662f\u79fb\u9664\u5f15\u7528\u548ccv\u7b26\uff0c\u5927\u5927\u7b80\u5316\u4e86\u6211\u4eec\u7684\u4e66\u5199\u3002\u9664\u4e86\u666e\u901a\u7c7b\u578b\u4e4b\u5916\uff0cstd::decay\u8fd8\u53ef\u4ee5\u7528\u4e8e\u6570\u7ec4\u548c\u51fd\u6570\uff0c\u5177\u4f53\u7684\u8f6c\u6362\u89c4\u5219\u662f\u8fd9\u6837\u7684\uff1a<\/p>\n<p>\u5148\u79fb\u9664T\u7c7b\u578b\u7684\u5f15\u7528\uff0c\u5f97\u5230\u7c7b\u578bU\uff0cU\u5b9a\u4e49\u4e3aremove_reference&lt;T&gt;::type\u3002<\/p>\n<ul>\n<li>\u5982\u679cis_array&lt;U&gt;::value\u4e3a true\uff0c\u4fee\u6539\u7c7b\u578btype\u4e3aremove_extent&lt;U&gt;::type *\u3002<\/li>\n<li>\u5426\u5219\uff0c\u5982\u679cis_function&lt;U&gt;::value\u4e3a true\uff0c\u4fee\u6539\u7c7b\u578btype\u5c06\u4e3aadd_pointer&lt;U&gt;::type\u3002<\/li>\n<li>\u5426\u5219\uff0c\u4fee\u6539\u7c7b\u578btype\u4e3a\u00a0remove_cv&lt;U&gt;::type\u3002<\/li>\n<\/ul>\n<p>std::decay\u7684\u57fa\u672c\u7528\u6cd5\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>typedef std::decay&lt;int&gt;::type A;           \/\/ int\r\ntypedef std::decay&lt;int&amp;&gt;::type B;          \/\/ int\r\ntypedef std::decay&lt;int&amp;&amp;&gt;::type C;         \/\/ int\r\ntypedef std::decay&lt;constint&amp;&gt;::type D;    \/\/ int\r\ntypedef std::decay&lt;int[2]&gt;::type E;        \/\/ int*\r\ntypedef std::decay&lt;int(int)&gt;::type F;      \/\/ int(*)(int)<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>std::decay\u9664\u4e86\u79fb\u9664\u666e\u901a\u7c7b\u578b\u7684cv\u7b26\u7684\u4f5c\u7528\u4e4b\u5916\uff0c\u8fd8\u53ef\u4ee5\u5c06\u51fd\u6570\u7c7b\u578b\u8f6c\u6362\u4e3a\u51fd\u6570\u6307\u9488\u7c7b\u578b\uff0c\u4ece\u800c\u5c06\u51fd\u6570\u6307\u9488\u53d8\u91cf\u4fdd\u5b58\u8d77\u6765\uff0c\u4ee5\u4fbf\u5728\u540e\u9762\u5ef6\u8fdf\u6267\u884c\uff0c\u6bd4\u5982\u4e0b\u9762\u7684\u4f8b\u5b50\u3002<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>template&lt;typename F&gt;\r\nstruct SimpFunction\r\n{\r\n    using FnType = typename std::decay&lt;F&gt;::type;\/\/\u5148\u79fb\u9664\u5f15\u7528\u518d\u6dfb\u52a0\u6307\u9488\r\n\r\n    SimpFunction(F&amp; f) : m_fn(f){}\r\n\r\n    void Run()\r\n    {\r\n        m_fn();\r\n    }\r\n\r\n    FnType m_fn;\r\n};<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>\u5982\u679c\u8981\u4fdd\u5b58\u8f93\u5165\u7684\u51fd\u6570\uff0c\u5219\u5148\u8981\u83b7\u53d6\u51fd\u6570\u5bf9\u5e94\u7684\u51fd\u6570\u6307\u9488\u7c7b\u578b\uff0c\u8fd9\u65f6\u5c31\u53ef\u4ee5\u7528std::decay\u6765\u83b7\u53d6\u51fd\u6570\u6307\u9488\u7c7b\u578b\u4e86\uff0cusing FnType = typename std::decay&lt;F&gt;::type;\u5b9e\u73b0\u51fd\u6570\u6307\u9488\u7c7b\u578b\u7684\u5b9a\u4e49\u3002type_traits\u8fd8\u63d0\u4f9b\u4e86\u83b7\u53d6\u53ef\u8c03\u7528\u5bf9\u8c61\u8fd4\u56de\u7c7b\u578b\u7684\u5143\u51fd\u6570\uff1astd::result_of\uff0c\u5b83\u7684\u57fa\u672c\u7528\u6cd5\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>int fn(int) {return int();}                            \/\/ function\r\ntypedef int(&amp;fn_ref)(int);                             \/\/ function reference\r\ntypedef int(*fn_ptr)(int);                             \/\/ function pointer\r\nstruct fn_class { int operator()(int i){return i;} };  \/\/ function-like class\r\n\r\nint main() {\r\n  typedef std::result_of&lt;decltype(fn)&amp;(int)&gt;::type A;  \/\/ int\r\n  typedef std::result_of&lt;fn_ref(int)&gt;::type B;         \/\/ int\r\n  typedef std::result_of&lt;fn_ptr(int)&gt;::type C;         \/\/ int\r\n  typedef std::result_of&lt;fn_class(int)&gt;::type D;       \/\/ int\r\n}<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>type_traits\u8fd8\u63d0\u4f9b\u4e86\u4e00\u4e2a\u5f88\u6709\u7528\u7684\u5143\u51fd\u6570std::enable_if\uff0c\u5b83\u5229\u7528SFINAE(substitude failure is not an error)\u7279\u6027\uff0c\u6839\u636e\u6761\u4ef6\u9009\u62e9\u91cd\u8f7d\u51fd\u6570\u7684\u5143\u51fd\u6570std::enable_if\uff0c\u5b83\u7684\u539f\u578b\u662f\uff1a<\/p>\n<p>template&lt;bool B, class T = void&gt; struct enable_if;<\/p>\n<p>\u6839\u636eenable_if\u7684\u5b57\u9762\u610f\u601d\u5c31\u53ef\u4ee5\u77e5\u9053\uff0c\u5b83\u4f7f\u5f97\u51fd\u6570\u5728\u5224\u65ad\u6761\u4ef6B\u4ec5\u4ec5\u4e3atrue\u65f6\u624d\u6709\u6548\uff0c\u5b83\u7684\u57fa\u672c\u7528\u6cd5\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>template &lt;class T&gt;\r\ntypename std::enable_if&lt;std::is_arithmetic&lt;T&gt;::value, T&gt;::type foo(T t)\r\n{\r\n    return t;\r\n}\r\nauto r = foo(1); \/\/\u8fd4\u56de\u6574\u65701\r\nauto r1 = foo(1.2); \/\/\u8fd4\u56de\u6d6e\u70b9\u65701.2\r\nauto r2 = foo(\u201ctest\u201d); \/\/compile error<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\u5bf9\u6a21\u677f\u53c2\u6570T\u505a\u4e86\u9650\u5b9a\uff0c\u5373\u53ea\u80fd\u662farithmetic\uff08\u6574\u578b\u548c\u6d6e\u70b9\u578b\uff09\u7c7b\u578b\uff0c\u5982\u679c\u4e3a\u975earithmetic\u7c7b\u578b\uff0c\u5219\u7f16\u8bd1\u4e0d\u901a\u8fc7\uff0c\u56e0\u4e3astd::enable_if\u53ea\u5bf9\u6ee1\u8db3\u5224\u65ad\u5f0f\u6761\u4ef6\u7684\u51fd\u6570\u6709\u6548\uff0c\u5bf9\u5176\u4ed6\u51fd\u6570\u65e0\u6548\u3002<\/p>\n<p>\u53ef\u4ee5\u901a\u8fc7enable_if\u6765\u5b9e\u73b0\u7f16\u8bd1\u671f\u7684if-else\u903b\u8f91\uff0c\u6bd4\u5982\u4e0b\u9762\u7684\u4f8b\u5b50\u901a\u8fc7enable_if\u548c\u6761\u4ef6\u5224\u65ad\u5f0f\u6765\u5c06\u5165\u53c2\u5206\u4e3a\u4e24\u5927\u7c7b\uff0c\u4ece\u800c\u6ee1\u8db3\u6240\u6709\u7684\u5165\u53c2\u7c7b\u578b\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>template &lt;class T&gt;\r\ntypename std::enable_if&lt;std::is_arithmetic&lt;T&gt;::value, int&gt;::type foo1(T t)\r\n{\r\n    cout &lt;&lt; t &lt;&lt; endl;\r\n    return 0;\r\n}\r\n\r\ntemplate &lt;class T&gt;\r\ntypename std::enable_if&lt;!std::is_arithmetic&lt;T&gt;::value, int&gt;::type foo1(T &amp;t)\r\n{\r\n    cout &lt;&lt; typeid(T).name() &lt;&lt; endl;\r\n    return 1;\r\n}<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>\u5bf9\u4e8earithmetic\u7c7b\u578b\u7684\u5165\u53c2\u5219\u8fd4\u56de0\uff0c\u5bf9\u4e8e\u975earithmetic\u7684\u7c7b\u578b\u5219\u8fd4\u56de1\uff0c\u901a\u8fc7arithmetic\u5c06\u6240\u6709\u7684\u5165\u53c2\u7c7b\u578b\u5206\u6210\u4e86\u4e24\u5927\u7c7b\u8fdb\u884c\u5904\u7406\u3002\u4ece\u4e0a\u9762\u7684\u4f8b\u5b50\u8fd8\u53ef\u4ee5\u770b\u5230\uff0cstd::enable_if\u53ef\u4ee5\u5b9e\u73b0\u5f3a\u5927\u7684\u91cd\u8f7d\u673a\u5236\uff0c\u56e0\u4e3a\u901a\u5e38\u5fc5\u987b\u662f\u53c2\u6570\u4e0d\u540c\u624d\u80fd\u91cd\u8f7d\uff0c\u5982\u679c\u53ea\u6709\u8fd4\u56de\u503c\u4e0d\u540c\u662f\u4e0d\u80fd\u91cd\u8f7d\u7684\uff0c\u800c\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c\u8fd4\u56de\u7c7b\u578b\u76f8\u540c\u7684\u51fd\u6570\u90fd\u53ef\u4ee5\u91cd\u8f7d\u3002<\/p>\n<p>C++11\u7684type_traits\u63d0\u4f9b\u4e86\u8fd1\u767e\u4e2a\u5728\u7f16\u8bd1\u671f\u8ba1\u7b97\u3001\u67e5\u8be2\u3001\u5224\u65ad\u3001\u8f6c\u6362\u548c\u9009\u62e9\u7684\u5143\u51fd\u6570\uff0c\u4e3a\u6211\u4eec\u7f16\u5199\u5143\u7a0b\u5e8f\u63d0\u4f9b\u4e86\u5f88\u5927\u7684\u4fbf\u5229\u3002\u5982\u679c\u8bf4C++11\u7684type_traits\u8ba9\u6a21\u7248\u5143\u7f16\u7a0b\u53d8\u5f97\u7b80\u5355\uff0c\u90a3\u4e48C++11\u63d0\u4f9b\u7684\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u548ctuple\u5219\u8fdb\u4e00\u6b65\u589e\u5f3a\u4e86\u6a21\u677f\u5143\u7f16\u7a0b\u3002<\/p>\n<h3>4.\u53ef\u53d8\u6a21\u677f\u53c2\u6570<\/h3>\n<p>C++11\u7684\u53ef\u53d8\u6a21\u7248\u53c2\u6570\uff08variadic templates\uff09\u662fC++11\u65b0\u589e\u7684\u6700\u5f3a\u5927\u7684\u7279\u6027\u4e4b\u4e00\uff0c\u5b83\u5bf9\u53c2\u6570\u8fdb\u884c\u4e86\u9ad8\u5ea6\u6cdb\u5316\uff0c\u5b83\u80fd\u8868\u793a0\u5230\u4efb\u610f\u4e2a\u6570\u3001\u4efb\u610f\u7c7b\u578b\u7684\u53c2\u6570\u3002\u5173\u4e8e\u5b83\u7684\u7528\u6cd5\u548c\u4f7f\u7528\u6280\u5de7\u8bfb\u8005\u53ef\u4ee5\u53c2\u8003\u7b14\u8005\u5728\u7a0b\u5e8f\u54582015\u5e742\u6708A\u4e0a\u7684\u6587\u7ae0\uff1a\u6cdb\u5316\u4e4b\u7f8e&#8211;C++11\u53ef\u53d8\u6a21\u7248\u53c2\u6570\u7684\u5999\u7528\uff0c\u8fd9\u91cc\u4e0d\u518d\u8d58\u8ff0\uff0c\u8fd9\u91cc\u5c06\u8981\u5c55\u793a\u7684\u5982\u4f55\u501f\u52a9\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u5b9e\u73b0\u4e00\u4e9b\u7f16\u8bd1\u671f\u7b97\u6cd5\uff0c\u6bd4\u5982\u83b7\u53d6\u6700\u5927\u503c\u3001\u5224\u65ad\u662f\u5426\u5305\u542b\u4e86\u67d0\u4e2a\u7c7b\u578b\u3001\u6839\u636e\u7d22\u5f15\u67e5\u627e\u7c7b\u578b\u3001\u83b7\u53d6\u7c7b\u578b\u7684\u7d22\u5f15\u548c\u904d\u5386\u7c7b\u578b\u7b49\u7b97\u6cd5\u3002\u5b9e\u73b0\u8fd9\u4e9b\u7b97\u6cd5\u9700\u8981\u7ed3\u5408type_traits\u6216\u5176\u5b83C++11\u7279\u6027\uff0c\u4e0b\u9762\u6765\u770b\u770b\u8fd9\u4e9b\u7f16\u8bd1\u671f\u7b97\u6cd5\u662f\u5982\u4f55\u5b9e\u73b0\u7684\u3002<\/p>\n<p>\u7f16\u8bd1\u671f\u4ece\u4e00\u4e2a\u6574\u5f62\u5e8f\u5217\u4e2d\u83b7\u53d6\u6700\u5927\u503c\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>\/\/\u83b7\u53d6\u6700\u5927\u7684\u6574\u6570\r\ntemplate &lt;size_t arg, size_t... rest&gt;\r\nstruct IntegerMax;\r\n\r\ntemplate &lt;size_t arg&gt;\r\nstruct IntegerMax&lt;arg&gt; : std::integral_constant&lt;size_t, arg&gt;\r\n{\r\n};\r\n\r\ntemplate &lt;size_t arg1, size_t arg2, size_t... rest&gt;\r\nstruct IntegerMax&lt;arg1, arg2, rest...&gt; : std::integral_constant&lt;size_t, arg1 &gt;= arg2 ? IntegerMax&lt;arg1, rest...&gt;::value :\r\n    IntegerMax&lt;arg2, rest...&gt;::value &gt;\r\n{\r\n};<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>\u8fd9\u4e2aIntegerMax\u7684\u5b9e\u73b0\u7528\u5230\u4e86type_traits\u4e2d\u7684std::integral_const\uff0c\u5b83\u5728\u5c55\u5f00\u53c2\u6570\u5305\u7684\u8fc7\u7a0b\u4e2d\uff0c\u4e0d\u65ad\u7684\u6bd4\u8f83\uff0c\u76f4\u5230\u6240\u6709\u7684\u53c2\u6570\u90fd\u6bd4\u8f83\u5b8c\uff0c\u6700\u7ec8std::integral_const\u7684value\u503c\u5373\u4e3a\u6700\u5927\u503c\u3002\u5b83\u7684\u4f7f\u7528\u5f88\u7b80\u5355\uff1a<\/p>\n<p>cout &lt;&lt; IntegerMax&lt;2, 5, 1, 7, 3&gt;::value &lt;&lt; endl; \/\/value\u4e3a7<\/p>\n<p>\u6211\u4eec\u53ef\u4ee5\u5728IntegerMax\u7684\u57fa\u7840\u4e0a\u8f7b\u677e\u7684\u5b9e\u73b0\u83b7\u53d6\u6700\u5927\u5185\u5b58\u5bf9\u9f50\u503c\u7684\u5143\u51fd\u6570MaxAlign\u3002<\/p>\n<p>\u7f16\u8bd1\u671f\u83b7\u53d6\u6700\u5927\u7684align\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>template&lt;typename... Args&gt;\r\nstruct MaxAlign : std::integral_constant&lt;int, IntegerMax&lt;std::alignment_of&lt;Args&gt;::value...&gt;::value&gt;{};\r\ncout &lt;&lt; MaxAlign&lt;int, short, double, char&gt;::value &lt;&lt; endl; \/\/value\u4e3a8\r\n    \u7f16\u8bd1\u5224\u65ad\u662f\u5426\u5305\u542b\u4e86\u67d0\u79cd\u7c7b\u578b\uff1a\r\ntemplate &lt; typename T, typename... List &gt;\r\nstruct Contains;\r\n\r\ntemplate &lt; typename T, typename Head, typename... Rest &gt;\r\nstruct Contains&lt;T, Head, Rest...&gt;\r\n    : std::conditional&lt; std::is_same&lt;T, Head&gt;::value, std::true_type, Contains&lt;T, Rest... &gt;&gt; ::type{};\r\n\r\ntemplate &lt; typename T &gt;\r\nstruct Contains&lt;T&gt; : std::false_type{};\r\n\u7528\u6cd5\uff1acout&lt;&lt;Contains&lt;int, char, double, int, short&gt;::value&lt;&lt;endl; \/\/\u8f93\u51fatrue<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>\u8fd9\u4e2aContains\u7684\u5b9e\u73b0\u7528\u5230\u4e86type_traits\u7684std::conditional\u3001std::is_same\u3001std::true_type\u548cstd::false_type\uff0c\u5b83\u7684\u5b9e\u73b0\u601d\u8def\u662f\u5728\u5c55\u5f00\u53c2\u6570\u5305\u7684\u8fc7\u7a0b\u4e2d\u4e0d\u65ad\u7684\u6bd4\u8f83\u7c7b\u578b\u662f\u5426\u76f8\u540c\uff0c\u5982\u679c\u76f8\u540c\u5219\u8bbe\u7f6e\u503c\u4e3atrue\uff0c\u5426\u5219\u8bbe\u7f6e\u4e3afalse\u3002<\/p>\n<p>\u7f16\u8bd1\u671f\u83b7\u53d6\u7c7b\u578b\u7684\u7d22\u5f15\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>template &lt; typename T, typename... List &gt;\r\nstruct IndexOf;\r\n\r\ntemplate &lt; typename T, typename Head, typename... Rest &gt;\r\nstruct IndexOf&lt;T, Head, Rest...&gt;\r\n{\r\n    enum{ value = IndexOf&lt;T, Rest...&gt;::value+1 };\r\n};\r\n\r\ntemplate &lt; typename T, typename... Rest &gt;\r\nstruct IndexOf&lt;T, T, Rest...&gt;\r\n{\r\n    enum{ value = 0 };\r\n};\r\n\r\ntemplate &lt; typename T &gt;\r\nstruct IndexOf&lt;T&gt;\r\n{\r\n    enum{value = -1};\r\n};<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>\u7528\u6cd5\uff1acout&lt;&lt; IndexOf&lt;int, double, short, char, int, float&gt;::value&lt;&lt;endl; \/\/\u8f93\u51fa3<\/p>\n<p>\u8fd9\u4e2aIndexOf\u7684\u5b9e\u73b0\u6bd4\u8f83\u7b80\u5355\uff0c\u5728\u5c55\u5f00\u53c2\u6570\u5305\u7684\u8fc7\u7a0b\u4e2d\u770b\u662f\u5426\u5339\u914d\u5230\u7279\u5316\u7684IndexOf&lt;T, T, Rest&#8230;&gt;\uff0c\u5982\u679c\u5339\u914d\u4e0a\u5219\u7ec8\u6b62\u9012\u5f52\u5c06\u4e4b\u524d\u7684value\u7d2f\u52a0\u8d77\u6765\u5f97\u5230\u76ee\u6807\u7c7b\u578b\u7684\u7d22\u5f15\u4f4d\u7f6e\uff0c\u5426\u5219\u5c06value\u52a01\uff0c\u5982\u679c\u6240\u6709\u7684\u7c7b\u578b\u4e2d\u90fd\u6ca1\u6709\u5bf9\u5e94\u7684\u7c7b\u578b\u5219\u8fd4\u56de-1\uff1b<\/p>\n<p>\u7f16\u8bd1\u671f\u6839\u636e\u7d22\u5f15\u4f4d\u7f6e\u67e5\u627e\u7c7b\u578b\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>template&lt;int index, typename... Types&gt;\r\nstruct At;\r\n\r\ntemplate&lt;int index, typename First, typename... Types&gt;\r\nstruct At&lt;index, First, Types...&gt;\r\n{\r\n    using type = typename At&lt;index - 1, Types...&gt;::type;\r\n};\r\n\r\ntemplate&lt;typename T, typename... Types&gt;\r\nstruct At&lt;0, T, Types...&gt;\r\n{\r\n    using type = T;\r\n};\r\n    \u7528\u6cd5\uff1a\r\nusing T = At&lt;1, int, double, char&gt;::type;\r\n    cout &lt;&lt; typeid(T).name() &lt;&lt; endl; \/\/\u8f93\u51fadouble<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>At\u7684\u5b9e\u73b0\u6bd4\u8f83\u7b80\u5355\uff0c\u53ea\u8981\u5728\u5c55\u5f00\u53c2\u6570\u5305\u7684\u8fc7\u7a0b\u4e2d\uff0c\u4e0d\u65ad\u7684\u5c06\u7d22\u5f15\u9012\u51cf\u81f30\u65f6\u4e3a\u6b62\u5373\u53ef\u83b7\u53d6\u5bf9\u5e94\u7d22\u5f15\u4f4d\u7f6e\u7684\u7c7b\u578b\u3002\u63a5\u4e0b\u6765\u770b\u770b\u5982\u4f55\u5728\u7f16\u8bd1\u671f\u904d\u5386\u7c7b\u578b\u3002<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>template&lt;typename T&gt;\r\nvoid printarg()\r\n{\r\n    cout &lt;&lt; typeid(T).name() &lt;&lt; endl;\r\n}\r\n\r\ntemplate&lt;typename... Args&gt;\r\nvoid for_each() \r\n{\r\n    std::initializer_list&lt;int&gt;{(printarg&lt;Args&gt;(), 0)...};\r\n}\r\n\u7528\u6cd5\uff1afor_each&lt;int,double&gt;();\/\/\u5c06\u8f93\u51faint double<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>\u8fd9\u91ccfor_each\u7684\u5b9e\u73b0\u662f\u901a\u8fc7\u521d\u59cb\u5316\u5217\u8868\u548c\u9017\u53f7\u8868\u8fbe\u5f0f\u6765\u904d\u5386\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u7684\u3002<\/p>\n<p>\u53ef\u4ee5\u770b\u5230\uff0c\u501f\u52a9\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u548ctype_traits\u4ee5\u53ca\u6a21\u677f\u504f\u7279\u5316\u548c\u9012\u5f52\u7b49\u65b9\u5f0f\u6211\u4eec\u53ef\u4ee5\u5b9e\u73b0\u4e00\u4e9b\u6709\u7528\u7684\u7f16\u8bd1\u671f\u7b97\u6cd5\uff0c\u8fd9\u4e9b\u7b97\u6cd5\u4e3a\u6211\u4eec\u7f16\u5199\u5e94\u7528\u5c42\u7ea7\u522b\u7684\u4ee3\u7801\u5960\u5b9a\u4e86\u57fa\u7840\uff0c\u540e\u9762\u6a21\u677f\u5143\u7f16\u7a0b\u7684\u5177\u4f53\u5e94\u7528\u4e2d\u5c06\u4f1a\u7528\u5230\u8fd9\u4e9b\u5143\u51fd\u6570\u3002<\/p>\n<p>C++11\u63d0\u4f9b\u7684tuple\u8ba9\u6211\u4eec\u7f16\u5199\u6a21\u7248\u5143\u7a0b\u5e8f\u53d8\u5f97\u66f4\u7075\u6d3b\u4e86\uff0c\u5728\u4e00\u5b9a\u7a0b\u5ea6\u4e0a\u589e\u5f3a\u4e86C++\u7684\u6cdb\u578b\u7f16\u7a0b\u80fd\u529b\uff0c\u4e0b\u9762\u6765\u770b\u770btuple\u5982\u4f55\u5e94\u7528\u4e8e\u5143\u7a0b\u5e8f\u4e2d\u7684\u3002<\/p>\n<h3>5.tuple\u4e0e\u6a21\u7248\u5143<\/h3>\n<p>C++11\u7684tuple\u672c\u8eab\u5c31\u662f\u4e00\u4e2a\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u7ec4\u6210\u7684\u5143\u51fd\u6570\uff0c\u5b83\u7684\u539f\u578b\u5982\u4e0b\uff1a<\/p>\n<p>template&lt;class&#8230;Types&gt;<br \/>\nclass tuple;<\/p>\n<p>tuple\u5728\u6a21\u7248\u5143\u7f16\u7a0b\u4e2d\u7684\u4e00\u4e2a\u5e94\u7528\u573a\u666f\u662f\u5c06\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u4fdd\u5b58\u8d77\u6765\uff0c\u56e0\u4e3a\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u4e0d\u80fd\u76f4\u63a5\u4f5c\u4e3a\u53d8\u91cf\u4fdd\u5b58\u8d77\u6765\uff0c\u9700\u8981\u501f\u52a9tuple\u4fdd\u5b58\u8d77\u6765\uff0c\u4fdd\u5b58\u4e4b\u540e\u518d\u5728\u9700\u8981\u7684\u65f6\u5019\u901a\u8fc7\u4e00\u4e9b\u624b\u6bb5\u5c06tuple\u53c8\u8f6c\u6362\u4e3a\u53ef\u53d8\u6a21\u677f\u53c2\u6570\uff0c\u8fd9\u4e2a\u8fc7\u7a0b\u6709\u70b9\u7c7b\u4f3c\u4e8e\u5316\u5b66\u4e2d\u7684\u201c\u6c27\u5316\u8fd8\u539f\u53cd\u5e94\u201d\u3002\u770b\u770b\u4e0b\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u548ctuple\u662f\u5982\u4f55\u76f8\u4e92\u8f6c\u6362\u7684\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>\/\/\u5b9a\u4e49\u6574\u5f62\u5e8f\u5217\r\ntemplate&lt;int...&gt;\r\nstruct IndexSeq{};\r\n\r\n\/\/\u751f\u6210\u6574\u5f62\u5e8f\u5217\r\ntemplate&lt;int N, int... Indexes&gt;\r\nstruct MakeIndexes : MakeIndexes&lt;N - 1, N - 1, Indexes...&gt;{};\r\n\r\ntemplate&lt;int... indexes&gt;\r\nstruct MakeIndexes&lt;0, indexes...&gt;{\r\n    typedef IndexSeq&lt;indexes...&gt; type;\r\n};\r\n\r\ntemplate&lt;typename... Args&gt;\r\nvoid printargs(Args... args){\r\n    \/\/\u5148\u5c06\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u4fdd\u5b58\u5230tuple\u4e2d\r\n    print_helper(typename MakeIndexes&lt;sizeof... (Args)&gt;::type(), std::make_tuple(args...));\r\n}\r\n\r\ntemplate&lt;int... Indexes, typename... Args&gt;\r\nvoid print_helper(IndexSeq&lt;Indexes...&gt;, std::tuple&lt;Args...&gt;&amp;&amp; tup){\r\n    \/\/\u518d\u5c06tuple\u8f6c\u6362\u4e3a\u53ef\u53d8\u6a21\u677f\u53c2\u6570\uff0c\u5c06\u53c2\u6570\u8fd8\u539f\u56de\u6765\uff0c\u518d\u8c03\u7528print\r\n    print(std::get&lt;Indexes&gt;(tup)...); \r\n}\r\ntemplate&lt;typename T&gt;\r\nvoid print(T t)\r\n{\r\n    cout &lt;&lt; t &lt;&lt; endl;\r\n}\r\n\r\ntemplate&lt;typename T, typename... Args&gt;\r\nvoid print(T t, Args... args)\r\n{\r\n    print(t);\r\n    print(args...);\r\n}<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>\u7528\u6cd5\uff1aprintargs(1, 2.5, \u201ctest\u201d); \/\/\u5c06\u8f93\u51fa1 2.5 test<\/p>\n<p>\u4e0a\u9762\u7684\u4f8b\u5b50print\u5b9e\u9645\u4e0a\u662f\u8f93\u51fa\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u7684\u5185\u5bb9\uff0c\u5177\u4f53\u505a\u6cd5\u662f\u5148\u5c06\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u4fdd\u5b58\u5230tuple\u4e2d\uff0c\u7136\u540e\u518d\u901a\u8fc7\u5143\u51fd\u6570MakeIndexes\u751f\u6210\u4e00\u4e2a\u6574\u5f62\u5e8f\u5217\uff0c\u8fd9\u4e2a\u6574\u5f62\u5e8f\u5217\u5c31\u662fIndexSeq&lt;0,1,2&gt;\uff0c\u6574\u5f62\u5e8f\u5217\u4ee3\u8868\u4e86tuple\u4e2d\u5143\u7d20\u7684\u7d22\u5f15\uff0c\u751f\u6210\u6574\u5f62\u5e8f\u5217\u4e4b\u540e\u518d\u8c03\u7528print_helper\uff0c\u5728print_helper\u4e2d\u5c55\u5f00\u8fd9\u4e2a\u6574\u5f62\u5e8f\u5217\uff0c\u5c55\u5f00\u7684\u8fc7\u7a0b\u4e2d\u6839\u636e\u5177\u4f53\u7684\u7d22\u5f15\u4ecetuple\u4e2d\u83b7\u53d6\u5bf9\u5e94\u7684\u5143\u7d20\uff0c\u6700\u7ec8\u5c06\u4ecetuple\u4e2d\u53d6\u51fa\u6765\u7684\u5143\u7d20\u7ec4\u6210\u4e00\u4e2a\u53ef\u53d8\u6a21\u677f\u53c2\u6570\uff0c\u4ece\u800c\u5b9e\u73b0\u4e86tuple\u201c\u8fd8\u539f\u201d\u4e3a\u53ef\u53d8\u6a21\u677f\u53c2\u6570\uff0c\u6700\u7ec8\u8c03\u7528print\u6253\u5370\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u3002<\/p>\n<p>tuple\u5728\u6a21\u677f\u5143\u7f16\u7a0b\u4e2d\u7684\u53e6\u5916\u4e00\u4e2a\u5e94\u7528\u573a\u666f\u662f\u7528\u6765\u5b9e\u73b0\u4e00\u4e9b\u7f16\u8bd1\u671f\u7b97\u6cd5\uff0c\u6bd4\u5982\u5e38\u89c1\u7684\u904d\u5386\u3001\u67e5\u627e\u548c\u5408\u5e76\u7b49\u7b97\u6cd5\uff0c\u5b9e\u73b0\u7684\u601d\u8def\u548c\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u5b9e\u73b0\u7684\u7f16\u8bd1\u671f\u7b97\u6cd5\u7c7b\u4f3c\uff0c\u5173\u4e8etuple\u76f8\u5173\u7684\u7b97\u6cd5\uff0c\u8bfb\u8005\u53ef\u4ee5\u53c2\u8003\u7b14\u8005\u5728github\u4e0a\u7684\u4ee3\u7801\uff1a<a href=\"https:\/\/github.com\/qicosmos\/cosmos\/tree\/master\/tuple\">https:\/\/github.com\/qicosmos\/cosmos\/tree\/master\/tuple<\/a>\u3002<\/p>\n<p>\u4e0b\u9762\u6765\u770b\u770b\u6a21\u7248\u5143\u7684\u5177\u4f53\u5e94\u7528\u3002<\/p>\n<h3>6.\u6a21\u7248\u5143\u7684\u5e94\u7528<\/h3>\n<p>\u6211\u4eec\u5c06\u5c55\u793a\u5982\u4f55\u901a\u8fc7\u6a21\u7248\u5143\u6765\u5b9e\u73b0function_traits\u548cVairant\u7c7b\u578b\u3002<\/p>\n<p>function_traits\u7528\u6765\u83b7\u53d6\u51fd\u6570\u8bed\u4e49\u7684\u53ef\u8c03\u7528\u5bf9\u8c61\u7684\u4e00\u4e9b\u5c5e\u6027\uff0c\u6bd4\u5982\u51fd\u6570\u7c7b\u578b\u3001\u8fd4\u56de\u7c7b\u578b\u3001\u51fd\u6570\u6307\u9488\u7c7b\u578b\u548c\u53c2\u6570\u7c7b\u578b\u7b49\u3002\u4e0b\u9762\u6765\u770b\u770b\u5982\u4f55\u5b9e\u73b0function_traits\u3002<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>template&lt;typename T&gt;\r\nstruct function_traits;\r\n\r\n\/\/\u666e\u901a\u51fd\u6570\r\ntemplate&lt;typename Ret, typename... Args&gt;\r\nstruct function_traits&lt;Ret(Args...)&gt;\r\n{\r\npublic:\r\n    enum { arity = sizeof...(Args) };\r\n    typedef Ret function_type(Args...);\r\n    typedef Ret return_type;\r\n    using stl_function_type = std::function&lt;function_type&gt;;\r\n    typedef Ret(*pointer)(Args...);\r\n\r\n    template&lt;size_t I&gt;\r\n    struct args\r\n    {\r\n        static_assert(I &lt; arity, \"index is out of range, index must less than sizeof Args\");\r\n        using type = typename std::tuple_element&lt;I, std::tuple&lt;Args...&gt;&gt;::type;\r\n    };\r\n};\r\n\r\n\/\/\u51fd\u6570\u6307\u9488\r\ntemplate&lt;typename Ret, typename... Args&gt;\r\nstruct function_traits&lt;Ret(*)(Args...)&gt; : function_traits&lt;Ret(Args...)&gt;{};\r\n\r\n\/\/std::function\r\ntemplate &lt;typename Ret, typename... Args&gt;\r\nstruct function_traits&lt;std::function&lt;Ret(Args...)&gt;&gt; : function_traits&lt;Ret(Args...)&gt;{};\r\n\r\n\/\/member function\r\n#define FUNCTION_TRAITS(...) \\\r\n    template &lt;typename ReturnType, typename ClassType, typename... Args&gt;\\\r\n    struct function_traits&lt;ReturnType(ClassType::*)(Args...) __VA_ARGS__&gt; : function_traits&lt;ReturnType(Args...)&gt;{}; \\\r\n\r\nFUNCTION_TRAITS()\r\nFUNCTION_TRAITS(const)\r\nFUNCTION_TRAITS(volatile)\r\nFUNCTION_TRAITS(const volatile)\r\n\r\n\/\/\u51fd\u6570\u5bf9\u8c61\r\ntemplate&lt;typename Callable&gt;\r\nstruct function_traits : function_traits&lt;decltype(&amp;Callable::operator())&gt;{};<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>\u7531\u4e8e\u53ef\u8c03\u7528\u5bf9\u8c61\u53ef\u80fd\u662f\u666e\u901a\u7684\u51fd\u6570\u3001\u51fd\u6570\u6307\u9488\u3001<span lang=\"EN-US\">lambda\u3001std::function\u548c\u6210\u5458\u51fd\u6570\uff0c\u6240\u4ee5\u6211\u4eec\u9700\u8981\u9488\u5bf9\u8fd9\u4e9b\u7c7b\u578b\u5206\u522b\u505a\u504f\u7279\u5316\u3002\u5176\u4e2d\uff0c\u6210\u5458\u51fd\u6570\u7684\u504f\u7279\u5316\u7a0d\u5fae\u590d\u6742\u4e00\u70b9\uff0c\u56e0\u4e3a\u6d89\u53ca\u5230cv\u7b26\u7684\u5904\u7406\uff0c\u8fd9\u91cc\u901a\u8fc7\u5b9a\u4e49\u4e00\u4e2a\u5b8f\u6765\u6d88\u9664\u91cd\u590d\u7684\u6a21\u677f\u7c7b\u5b9a\u4e49\u3002\u53c2\u6570\u7c7b\u578b\u7684\u83b7\u53d6\u6211\u4eec\u662f\u501f\u52a9\u4e8etuple\uff0c\u5c06\u53c2\u6570\u8f6c\u6362\u4e3atuple\u7c7b\u578b\uff0c\u7136\u540e\u6839\u636e\u7d22\u5f15\u6765\u83b7\u53d6\u5bf9\u5e94\u7c7b\u578b\u3002\u5b83\u7684\u7528\u6cd5\u6bd4\u8f83\u7b80\u5355\uff1a<\/span><\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>template&lt;typename T&gt;\r\nvoid PrintType()\r\n{\r\n    cout &lt;&lt; typeid(T).name() &lt;&lt; endl;\r\n}\r\nint main()\r\n{\r\n    std::function&lt;int(int)&gt; f = [](int a){return a; };\r\n    PrintType&lt;function_traits&lt;std::function&lt;int(int)&gt;&gt;::function_type&gt;(); \/\/\u5c06\u8f93\u51faint __cdecl(int)\r\n    PrintType&lt;function_traits&lt;std::function&lt;int(int)&gt;&gt;::args&lt;0&gt;::type&gt;();\/\/\u5c06\u8f93\u51faint\r\n    PrintType&lt;function_traits&lt;decltype(f)&gt;::function_type&gt;();\/\/\u5c06\u8f93\u51faint __cdecl(int)\r\n}<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p>\u6709\u4e86\u8fd9\u4e2afunction_traits\u548c\u524d\u9762\u5b9e\u73b0\u7684\u4e00\u4e9b\u5143\u51fd\u6570\uff0c\u6211\u4eec\u5c31\u80fd\u65b9\u4fbf\u7684\u5b9e\u73b0\u4e00\u4e2a\u201c\u4e07\u80fd\u7c7b\u578b\u201d\u2014Variant\uff0cVariant\u5b9e\u9645\u4e0a\u4e00\u4e2a\u6cdb\u5316\u7684\u7c7b\u578b\uff0c\u8fd9\u4e2aVariant\u548cboost.variant\u7684\u7528\u6cd5\u7c7b\u4f3c\u3002boost.variant\u7684\u57fa\u672c\u7528\u6cd5\u5982\u4e0b\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<pre>typedef variant&lt;int,char, double&gt; vt;\r\nvt v = 1;\r\nv = 'a';\r\nv = 12.32;<\/pre>\n<\/div>\n<p>\u8fd9\u4e2avariant\u53ef\u4ee5\u63a5\u53d7\u5df2\u7ecf\u5b9a\u4e49\u7684\u90a3\u4e9b\u7c7b\u578b\uff0c\u770b\u8d77\u6765\u6709\u70b9\u7c7b\u4f3c\u4e8ec#\u548cjava\u4e2d\u7684object\u7c7b\u578b\uff0c\u5b9e\u9645\u4e0avariant\u662f\u64e6\u9664\u4e86\u7c7b\u578b\uff0c\u8981\u83b7\u53d6\u5b83\u7684\u5b9e\u9645\u7c7b\u578b\u7684\u65f6\u5019\u5c31\u7a0d\u663e\u9ebb\u70e6\uff0c\u9700\u8981\u901a\u8fc7boost.visitor\u6765\u8bbf\u95ee\uff1a<\/p>\n<div class=\"cnblogs_code\"><img decoding=\"async\" id=\"code_img_closed_166b6469-2a75-458a-bc9a-ec1e1b874545\" class=\"code_img_closed\" src=\"https:\/\/images.cnblogs.com\/OutliningIndicators\/ContractedBlock.gif\" alt=\"\" \/><img decoding=\"async\" id=\"code_img_opened_166b6469-2a75-458a-bc9a-ec1e1b874545\" class=\"code_img_opened\" src=\"https:\/\/images.cnblogs.com\/OutliningIndicators\/ExpandedBlockStart.gif\" alt=\"\" \/><\/p>\n<div id=\"cnblogs_code_open_166b6469-2a75-458a-bc9a-ec1e1b874545\" class=\"cnblogs_code_hide\">\n<pre>struct VariantVisitor : public boost::static_visitor&lt;void&gt;\r\n{\r\n    void operator() (int a)\r\n    {\r\n        cout &lt;&lt; \"int\" &lt;&lt; endl;\r\n    }\r\n\r\n    void operator() (short val)\r\n    {\r\n        cout &lt;&lt; \"short\" &lt;&lt; endl;\r\n    }\r\n\r\n    void operator() (double val)\r\n    {\r\n        cout &lt;&lt; \"double\" &lt;&lt; endl;\r\n    }\r\n\r\n    void operator() (std::string val)\r\n    {\r\n        cout &lt;&lt; \"string\" &lt;&lt; endl;\r\n    }\r\n};\r\n\r\nboost::variant&lt;int,short,double,std::string&gt; v = 1;\r\nboost::apply_visitor(visitor, v); \/\/\u5c06\u8f93\u51faint<\/pre>\n<\/div>\n<p><span class=\"cnblogs_code_collapse\">View Code<\/span><\/div>\n<p>\u901a\u8fc7C++11\u6a21\u7248\u5143\u5b9e\u73b0\u7684Variant\u5c06\u6539\u8fdb\u503c\u7684\u83b7\u53d6\uff0c\u5c06\u83b7\u53d6\u5b9e\u9645\u503c\u7684\u65b9\u5f0f\u6539\u4e3a\u5185\u7f6e\u7684\uff0c\u5373\u901a\u8fc7\u4e0b\u9762\u7684\u65b9\u5f0f\u6765\u8bbf\u95ee\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<pre>typedef Variant&lt;int, double, string, int&gt; cv;\r\ncv v = 10;\r\nv.Visit([&amp;](double i){cout &lt;&lt; i &lt;&lt; endl; }, [](short i){cout &lt;&lt; i &lt;&lt; endl; }, [=](int i){cout &lt;&lt; i &lt;&lt; endl; },[](const string&amp; i){cout &lt;&lt; i &lt;&lt; endl; });\/\/\u7ed3\u679c\u5c06\u8f93\u51fa10<\/pre>\n<\/div>\n<p>\u8fd9\u79cd\u65b9\u5f0f\u66f4\u65b9\u4fbf\u76f4\u89c2\u3002Variant\u7684\u5b9e\u73b0\u9700\u8981\u501f\u52a9\u524d\u6587\u4e2d\u5b9e\u73b0\u7684\u4e00\u4e9b\u5143\u51fd\u6570MaxInteger\u3001MaxAlign\u3001Contains\u548cAt\u7b49\u7b49\u3002\u4e0b\u9762\u6765\u770b\u770bVariant\u5b9e\u73b0\u7684\u5173\u952e\u4ee3\u7801\uff0c\u5b8c\u6574\u7684\u4ee3\u7801\u8bf7\u8bfb\u8005\u53c2\u8003\u7b14\u8005\u5728github\u4e0a\u7684\u4ee3\u7801<a href=\"https:\/\/github.com\/qicosmos\/cosmos\/blob\/master\/Varaint.hpp\">https:\/\/github.com\/qicosmos\/cosmos\/blob\/master\/Varaint.hpp<\/a>\u3002<\/p>\n<div class=\"cnblogs_code\"><img decoding=\"async\" id=\"code_img_closed_ab0414c2-68ae-43e2-a77f-c141dd775cb9\" class=\"code_img_closed\" src=\"https:\/\/images.cnblogs.com\/OutliningIndicators\/ContractedBlock.gif\" alt=\"\" \/><img decoding=\"async\" id=\"code_img_opened_ab0414c2-68ae-43e2-a77f-c141dd775cb9\" class=\"code_img_opened\" src=\"https:\/\/images.cnblogs.com\/OutliningIndicators\/ExpandedBlockStart.gif\" alt=\"\" \/><\/p>\n<div id=\"cnblogs_code_open_ab0414c2-68ae-43e2-a77f-c141dd775cb9\" class=\"cnblogs_code_hide\">\n<pre>template&lt;typename... Types&gt;\r\nclass Variant{\r\n    enum{\r\n        data_size = IntegerMax&lt;sizeof(Types)...&gt;::value,\r\n        align_size = MaxAlign&lt;Types...&gt;::value\r\n    };\r\n    using data_t = typename std::aligned_storage&lt;data_size, align_size&gt;::type;\r\npublic:\r\n    template&lt;int index&gt;\r\n    using IndexType = typename At&lt;index, Types...&gt;::type;\r\n\r\n    Variant(void) :m_typeIndex(typeid(void)){}\r\n    ~Variant(){ Destroy(m_typeIndex, &amp;m_data); }\r\n\r\n    Variant(Variant&lt;Types...&gt;&amp;&amp; old) : m_typeIndex(old.m_typeIndex){\r\n        Move(old.m_typeIndex, &amp;old.m_data, &amp;m_data);\r\n    }\r\n\r\n    Variant(const Variant&lt;Types...&gt;&amp; old) : m_typeIndex(old.m_typeIndex){\r\n        Copy(old.m_typeIndex, &amp;old.m_data, &amp;m_data);\r\n    }\r\n\r\n    template &lt;class T,\r\n    class = typename std::enable_if&lt;Contains&lt;typename std::remove_reference&lt;T&gt;::type, Types...&gt;::value&gt;::type&gt; Variant(T&amp;&amp; value) : m_typeIndex(typeid(void)){\r\n            Destroy(m_typeIndex, &amp;m_data);\r\n            typedef typename std::remove_reference&lt;T&gt;::type U;\r\n            new(&amp;m_data) U(std::forward&lt;T&gt;(value));\r\n            m_typeIndex = type_index(typeid(U));\r\n    }\r\n\r\n    template&lt;typename T&gt;\r\n    bool Is() const{\r\n        return (m_typeIndex == type_index(typeid(T)));\r\n    }\r\n\r\n    template&lt;typename T&gt;\r\n    typename std::decay&lt;T&gt;::type&amp; Get(){\r\n        using U = typename std::decay&lt;T&gt;::type;\r\n        if (!Is&lt;U&gt;())\r\n        {\r\n            cout &lt;&lt; typeid(U).name() &lt;&lt; \" is not defined. \" &lt;&lt; \"current type is \" &lt;&lt;\r\n                m_typeIndex.name() &lt;&lt; endl;\r\n            throw std::bad_cast();\r\n        }\r\n\r\n        return *(U*)(&amp;m_data);\r\n    }\r\n\r\n    template&lt;typename F&gt;\r\n    void Visit(F&amp;&amp; f){\r\n        using T = typename Function_Traits&lt;F&gt;::template arg&lt;0&gt;::type;\r\n        if (Is&lt;T&gt;())\r\n            f(Get&lt;T&gt;());\r\n    }\r\n\r\n    template&lt;typename F, typename... Rest&gt;\r\n    void Visit(F&amp;&amp; f, Rest&amp;&amp;... rest){\r\n        using T = typename Function_Traits&lt;F&gt;::template arg&lt;0&gt;::type;\r\n        if (Is&lt;T&gt;())\r\n            Visit(std::forward&lt;F&gt;(f));\r\n        else\r\n            Visit(std::forward&lt;Rest&gt;(rest)...);\r\n    }\r\nprivate:\r\n    void Destroy(const type_index&amp; index, void * buf){\r\n        std::initializer_list&lt;int&gt;{(Destroy0&lt;Types&gt;(index, buf), 0)...};\r\n    }\r\n\r\n    template&lt;typename T&gt;\r\n    void Destroy0(const type_index&amp; id, void* data){\r\n        if (id == type_index(typeid(T)))\r\n            reinterpret_cast&lt;T*&gt;(data)-&gt;~T();\r\n    }\r\n\r\n    void Move(const type_index&amp; old_t, void* old_v, void* new_v) {\r\n        std::initializer_list&lt;int&gt;{(Move0&lt;Types&gt;(old_t, old_v, new_v), 0)...};\r\n    }\r\n\r\n    template&lt;typename T&gt;\r\n    void Move0(const type_index&amp; old_t, void* old_v, void* new_v){\r\n        if (old_t == type_index(typeid(T)))\r\n            new (new_v)T(std::move(*reinterpret_cast&lt;T*&gt;(old_v)));\r\n    }\r\n\r\n    void Copy(const type_index&amp; old_t, void* old_v, void* new_v){\r\n        std::initializer_list&lt;int&gt;{(Copy0&lt;Types&gt;(old_t, old_v, new_v), 0)...};\r\n    }\r\n\r\n    template&lt;typename T&gt;\r\n    void Copy0(const type_index&amp; old_t, void* old_v, void* new_v){\r\n        if (old_t == type_index(typeid(T)))\r\n            new (new_v)T(*reinterpret_cast&lt;const T*&gt;(old_v));\r\n    }\r\nprivate:\r\n    data_t m_data;\r\n    std::type_index m_typeIndex;\/\/\u7c7b\u578bID\r\n};<\/pre>\n<\/div>\n<p><span class=\"cnblogs_code_collapse\">View Code<\/span><\/div>\n<p align=\"left\">\u3000\u3000\u5b9e\u73b0Variant\u9996\u5148\u9700\u8981\u5b9a\u4e49\u4e00\u4e2a\u8db3\u591f\u5927\u7684\u7f13\u51b2\u533a\u7528\u6765\u5b58\u653e\u4e0d\u540c\u7684\u7c7b\u578b\u7684\u503c\uff0c\u8fd9\u4e2a\u7f13\u7c7b\u578b\u51b2\u533a\u5b9e\u9645\u4e0a\u5c31\u662f\u7528\u6765\u64e6\u9664\u7c7b\u578b\uff0c\u4e0d\u540c\u7684\u7c7b\u578b\u90fd\u901a\u8fc7placement new\u5728\u8fd9\u4e2a\u7f13\u51b2\u533a\u4e0a\u521b\u5efa\u5bf9\u8c61\uff0c\u56e0\u4e3a\u7c7b\u578b\u957f\u5ea6\u4e0d\u540c\uff0c\u6240\u4ee5\u9700\u8981\u8003\u8651\u5185\u5b58\u5bf9\u9f50\uff0cC++11\u521a\u597d\u63d0\u4f9b\u4e86\u5185\u5b58\u5bf9\u9f50\u7684\u7f13\u51b2\u533aaligned_storage\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<pre>template&lt; std::size_t Len, std::size_t Align = \/*default-alignment*\/ &gt;\r\nstruct aligned_storage;<\/pre>\n<\/div>\n<p align=\"left\">\u3000\u3000\u5b83\u7684\u7b2c\u4e00\u4e2a\u53c2\u6570\u662f\u7f13\u51b2\u533a\u7684\u957f\u5ea6\uff0c\u7b2c\u4e8c\u4e2a\u53c2\u6570\u662f\u7f13\u51b2\u533a\u5185\u5b58\u5bf9\u9f50\u7684\u5927\u5c0f\uff0c\u7531\u4e8eVaraint\u53ef\u4ee5\u63a5\u53d7\u591a\u79cd\u7c7b\u578b\uff0c\u6240\u4ee5\u6211\u4eec\u9700\u8981\u83b7\u53d6\u6700\u5927\u7684\u7c7b\u578b\u957f\u5ea6\uff0c\u4fdd\u8bc1\u7f13\u51b2\u533a\u8db3\u591f\u5927\uff0c\u7136\u540e\u8fd8\u8981\u83b7\u53d6\u6700\u5927\u7684\u5185\u5b58\u5bf9\u9f50\u5927\u5c0f\uff0c\u8fd9\u91cc\u6211\u4eec\u901a\u8fc7\u524d\u9762\u5b9e\u73b0\u7684MaxInteger\u548cMaxAlign\u5c31\u53ef\u4ee5\u4e86\uff0cVaraint\u4e2d\u5185\u5b58\u5bf9\u9f50\u7684\u7f13\u51b2\u533a\u5b9a\u4e49\u5982\u4e0b\uff1a<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>enum\r\n{\r\n    data_size = IntegerMax&lt;sizeof(Types)...&gt;::value,\r\n    align_size = MaxAlign&lt;Types...&gt;::value\r\n};\r\nusing data_t = typename std::aligned_storage&lt;data_size, align_size&gt;::type; \/\/\u5185\u5b58\u5bf9\u9f50\u7684\u7f13\u51b2\u533a\u7c7b\u578b<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p align=\"left\">\u3000\u3000\u5176\u6b21\uff0c\u6211\u4eec\u8fd8\u8981\u5b9e\u73b0\u5bf9\u7f13\u51b2\u533a\u7684\u6784\u9020\u3001\u62f7\u8d1d\u3001\u6790\u6784\u548c\u79fb\u52a8\uff0c\u56e0\u4e3aVariant\u91cd\u65b0\u8d4b\u503c\u7684\u65f6\u5019\u9700\u8981\u5c06\u7f13\u51b2\u533a\u4e2d\u539f\u6765\u7684\u7c7b\u578b\u6790\u6784\u6389\uff0c\u62f7\u8d1d\u6784\u9020\u548c\u79fb\u52a8\u6784\u9020\u65f6\u5219\u9700\u8981\u62f7\u8d1d\u548c\u79fb\u52a8\u3002\u8fd9\u91cc\u4ee5\u6790\u6784\u4e3a\u4f8b\uff0c\u6211\u4eec\u9700\u8981\u6839\u636e\u5f53\u524d\u7684type_index\u6765\u904d\u5386Variant\u7684\u6240\u6709\u7c7b\u578b\uff0c\u627e\u5230\u5bf9\u5e94\u7684\u7c7b\u578b\u7136\u540e\u8c03\u7528\u8be5\u7c7b\u578b\u7684\u6790\u6784\u51fd\u6570\u3002<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>void Destroy(const type_index&amp; index, void * buf)\r\n    {\r\n        std::initializer_list&lt;int&gt;{(Destroy0&lt;Types&gt;(index, buf), 0)...};\r\n    }\r\n\r\n    template&lt;typename T&gt;\r\n    void Destroy0(const type_index&amp; id, void* data)\r\n    {\r\n        if (id == type_index(typeid(T)))\r\n            reinterpret_cast&lt;T*&gt;(data)-&gt;~T();\r\n    }<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p align=\"left\">\u3000\u3000\u8fd9\u91cc\uff0c\u6211\u4eec\u901a\u8fc7\u521d\u59cb\u5316\u5217\u8868\u548c\u9017\u53f7\u8868\u8fbe\u5f0f\u6765\u5c55\u5f00\u53ef\u53d8\u6a21\u677f\u53c2\u6570\uff0c\u5728\u5c55\u5f00\u7684\u8fc7\u7a0b\u4e2d\u67e5\u627e\u5bf9\u5e94\u7684\u7c7b\u578b\uff0c\u5982\u679c\u627e\u5230\u4e86\u5219\u6790\u6784\u3002\u5728Variant\u6784\u9020\u65f6\u8fd8\u9700\u8981\u6ce8\u610f\u4e00\u4e2a\u7ec6\u8282\u662f\uff0cVariant\u4e0d\u80fd\u63a5\u53d7\u6ca1\u6709\u9884\u5148\u5b9a\u4e49\u7684\u7c7b\u578b\uff0c\u6240\u4ee5\u5728\u6784\u9020Variant\u65f6\uff0c\u9700\u8981\u9650\u5b9a\u7c7b\u578b\u5fc5\u987b\u5728\u9884\u5b9a\u4e49\u7684\u7c7b\u578b\u8303\u56f4\u5f53\u4e2d\uff0c\u8fd9\u91cc\u901a\u8fc7type_traits\u7684enable_if\u6765\u9650\u5b9a\u6a21\u677f\u53c2\u6570\u7684\u7c7b\u578b\u3002<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>template &lt;class T,\r\n    class = typename std::enable_if&lt;Contains&lt;typename std::remove_reference&lt;T&gt;::type, Types...&gt;::value&gt;::type&gt; Variant(T&amp;&amp; value) : m_typeIndex(typeid(void)){\r\n            Destroy(m_typeIndex, &amp;m_data);\r\n            typedef typename std::remove_reference&lt;T&gt;::type U;\r\n            new(&amp;m_data) U(std::forward&lt;T&gt;(value));\r\n            m_typeIndex = type_index(typeid(U));\r\n    }<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p align=\"left\">\u3000\u3000\u8fd9\u91ccenbale_if\u7684\u6761\u4ef6\u5c31\u662f\u524d\u9762\u5b9e\u73b0\u7684\u5143\u51fd\u6570Contains\u7684\u503c\uff0c\u5f53\u6ca1\u6709\u5728\u9884\u5b9a\u4e49\u7684\u7c7b\u578b\u4e2d\u627e\u5230\u5bf9\u5e94\u7684\u7c7b\u578b\u65f6\uff0c\u5373Contains\u8fd4\u56defalse\u65f6\uff0c\u7f16\u8bd1\u671f\u4f1a\u62a5\u4e00\u4e2a\u7f16\u8bd1\u9519\u8bef\u3002<\/p>\n<p align=\"left\">\u3000\u3000\u6700\u540e\u8fd8\u9700\u8981\u5b9e\u73b0\u5185\u7f6e\u7684Vistit\u529f\u80fd\uff0cVisit\u7684\u5b9e\u73b0\u9700\u8981\u5148\u901a\u8fc7\u5b9a\u4e49\u4e00\u7cfb\u5217\u7684\u8bbf\u95ee\u51fd\u6570\uff0c\u7136\u540e\u518d\u904d\u5386\u8fd9\u4e9b\u51fd\u6570\uff0c\u904d\u5386\u8fc7\u7a0b\u4e2d\uff0c\u5224\u65ad\u51fd\u6570\u7684\u7b2c\u4e00\u4e2a\u53c2\u6570\u7c7b\u578b\u7684type_index\u662f\u5426\u4e0e\u5f53\u524d\u7684type_index\u76f8\u540c\uff0c\u5982\u679c\u76f8\u540c\u5219\u83b7\u53d6\u5f53\u524d\u7c7b\u578b\u7684\u503c\u3002<\/p>\n<div class=\"cnblogs_code\">\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<pre>template&lt;typename F&gt;\r\n    void Visit(F&amp;&amp; f){\r\n        using T = typename Function_Traits&lt;F&gt;::template arg&lt;0&gt;::type;\r\n        if (Is&lt;T&gt;())\r\n            f(Get&lt;T&gt;());\r\n    }\r\n\r\n    template&lt;typename F, typename... Rest&gt;\r\n    void Visit(F&amp;&amp; f, Rest&amp;&amp;... rest){\r\n        using T = typename Function_Traits&lt;F&gt;::template arg&lt;0&gt;::type;\r\n        if (Is&lt;T&gt;())\r\n            Visit(std::forward&lt;F&gt;(f));\r\n        else\r\n            Visit(std::forward&lt;Rest&gt;(rest)...);\r\n    }<\/pre>\n<div class=\"cnblogs_code_toolbar\"><span class=\"cnblogs_code_copy\"><a title=\"\u590d\u5236\u4ee3\u7801\"><img decoding=\"async\" src=\"\/\/common.cnblogs.com\/images\/copycode.gif\" alt=\"\u590d\u5236\u4ee3\u7801\" \/><\/a><\/span><\/div>\n<\/div>\n<p align=\"left\">\u3000\u3000Visit\u529f\u80fd\u7684\u5b9e\u73b0\u5229\u7528\u4e86\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u548cfunction_traits\uff0c\u901a\u8fc7\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u6765\u904d\u5386\u4e00\u7cfb\u5217\u7684\u8bbf\u95ee\u51fd\u6570\uff0c\u904d\u5386\u8fc7\u7a0b\u4e2d\uff0c\u901a\u8fc7function_traits\u6765\u83b7\u53d6\u7b2c\u4e00\u4e2a\u53c2\u6570\u7684\u7c7b\u578b\uff0c\u548cVariant\u5f53\u524d\u7684type_index\u76f8\u540c\u7684\u5219\u53d6\u503c\u3002\u4e3a\u4ec0\u4e48\u8981\u83b7\u53d6\u8bbf\u95ee\u51fd\u6570\u7b2c\u4e00\u4e2a\u53c2\u6570\u7684\u7c7b\u578b\u5462\uff1f\u56e0\u4e3aVariant\u7684\u503c\u662f\u552f\u4e00\u7684\uff0c\u53ea\u6709\u4e00\u4e2a\u503c\uff0c\u6240\u4ee5\u83b7\u53d6\u7684\u8bbf\u95ee\u51fd\u6570\u7684\u7b2c\u4e00\u4e2a\u53c2\u6570\u7684\u7c7b\u578b\u5c31\u662fVariant\u4e2d\u5b58\u50a8\u7684\u5bf9\u8c61\u7684\u5b9e\u9645\u7c7b\u578b\u3002<\/p>\n<h3>7\u603b\u7ed3<\/h3>\n<p align=\"left\">\u3000\u3000C++11\u4e2d\u7684\u4e00\u4e9b\u7279\u6027\u6bd4\u5982type_traits\u3001\u53ef\u53d8\u6a21\u677f\u53c2\u6570\u548ctuple\u8ba9\u6a21\u7248\u5143\u7f16\u7a0b\u53d8\u5f97\u66f4\u7b80\u5355\u4e5f\u66f4\u5f3a\u5927\uff0c\u6a21\u7248\u5143\u7f16\u7a0b\u867d\u7136\u529f\u80fd\u5f3a\u5927\uff0c\u4f46\u4e5f\u6bd4\u8f83\u590d\u6742\uff0c\u8981\u7528\u597d\u6a21\u7248\u5143\uff0c\u9700\u8981\u6211\u4eec\u8f6c\u53d8\u601d\u7ef4\u65b9\u5f0f\uff0c\u5728\u638c\u63e1\u57fa\u672c\u7684\u7406\u8bba\u7684\u57fa\u7840\u4e0a\uff0c\u518d\u8ba4\u771f\u63e3\u6469\u6a21\u7248\u5143\u7684\u4e00\u4e9b\u5e38\u7528\u6280\u5de7\uff0c\u8fd9\u4e9b\u6280\u5de7\u662f\u6709\u89c4\u5f8b\u53ef\u5faa\u7684\uff0c\u57fa\u672c\u4e0a\u90fd\u662f\u901a\u8fc7\u91cd\u5b9a\u4e49\u3001\u9012\u5f52\u548c\u504f\u7279\u5316\u7b49\u624b\u6cd5\u6765\u5b9e\u73b0\u7684\uff0c\u5f53\u6211\u4eec\u5bf9\u8fd9\u4e9b\u57fa\u672c\u6280\u5de7\u5f88\u719f\u6089\u7684\u65f6\u5019\u518d\u7ed3\u5408\u4e0d\u65ad\u5730\u5b9e\u8df5\uff0c\u76f8\u4fe1\u5bf9\u6a21\u7248\u5143\u7f16\u7a0b\u5c31\u80fd\u505a\u5230\u201c\u6e38\u5203\u6709\u4f59\u201d\u4e86\u3002<\/p>\n<p align=\"left\">\n<p class=\"p0\"><strong>\u672c\u6587\u66fe\u53d1\u8868\u4e8e\u300a\u7a0b\u5e8f\u5458\u300b2015\u5e743\u6708\u520a\u3002\u8f6c\u8f7d\u8bf7\u6ce8\u660e\u51fa\u5904\u3002<\/strong><\/p>\n<p class=\"p0\"><strong>\u540e\u8bb0\uff1a<\/strong>\u672c\u6587\u7684\u5185\u5bb9\u4e3b\u8981\u6765\u81ea\u4e8e\u6211\u5728\u516c\u53f8\u5185\u90e8\u57f9\u8bad\u7684\u4e00\u6b21\u8bfe\u7a0b\uff0c\u56e0\u4e3a\u5f88\u591a\u4eba\u5bf9C++11\u6a21\u677f\u5143\u7f16\u7a0b\u7406\u89e3\u5f97\u4e0d\u6df1\u5165\uff0c\u6240\u4ee5\u6211\u89c9\u5f97\u6709\u5fc5\u8981\u62ff\u51fa\u6765\u5206\u4eab\u4e00\u4e0b\uff0c\u8ba9\u66f4\u591a\u7684\u4eba\u770b\u5230\uff0c\u5c31\u6574\u7406\u4e86\u4e00\u4e0b\u53d1\u5230\u7a0b\u5e8f\u5458\u6742\u5fd7\u4e86\uff0c\u6211\u76f8\u4fe1\u8bfb\u8005\u770b\u5b8c\u4e4b\u540e\u5bf9\u6a21\u7248\u5143\u4f1a\u6709\u5168\u9762\u6df1\u5165\u7684\u4e86\u89e3\u3002<\/p>\n<\/div>\n<div id=\"MySignature\">\u4e00\u70b9\u68a6\u60f3\uff1a\u5c3d\u81ea\u5df1\u4e00\u4efd\u529b\uff0c\u8ba9c++\u7684\u4e16\u754c\u53d8\u5f97\u66f4\u7f8e\u597d\uff01<\/div>\n<div class=\"clear\"><\/div>\n<div id=\"blog_post_info_block\">\n<div id=\"BlogPostCategory\">\u5206\u7c7b: <a href=\"https:\/\/www.cnblogs.com\/qicosmos\/category\/466797.html\" target=\"_blank\" rel=\"noopener\">C++ <\/a>, <a href=\"https:\/\/www.cnblogs.com\/qicosmos\/category\/490693.html\" target=\"_blank\" rel=\"noopener\">c++11 \u4f7f\u7528c++11\u6539\u8fdb\u6211\u4eec\u7684\u7a0b\u5e8f\u7cfb\u5217<\/a><\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>\u539f\u6587\u5730\u5740 &nbsp; 1.\u6982\u8ff0 \u6a21\u7248\u5143<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"colormag_page_container_layout":"default_layout","colormag_page_sidebar_layout":"default_layout","footnotes":""},"categories":[],"tags":[119],"class_list":["post-5536","post","type-post","status-publish","format-standard","hentry","tag-03-"],"_links":{"self":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts\/5536","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/comments?post=5536"}],"version-history":[{"count":0,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts\/5536\/revisions"}],"wp:attachment":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/media?parent=5536"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/categories?post=5536"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/tags?post=5536"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}