{"id":269,"date":"2022-09-20T09:33:40","date_gmt":"2022-09-20T01:33:40","guid":{"rendered":"http:\/\/139.224.63.49\/?p=269"},"modified":"2022-09-20T09:33:40","modified_gmt":"2022-09-20T01:33:40","slug":"c%e4%b8%adrange-based-loop%e4%b8%ad%e7%9a%84%e7%a9%b6%e7%ab%9f%e6%84%8f%e5%91%b3%e7%9d%80%e4%bb%80%e4%b9%88","status":"publish","type":"post","link":"http:\/\/iamnear.top\/?p=269","title":{"rendered":"c++\u4e2drange based loop\u4e2d\u7684&&\u7a76\u7adf\u610f\u5473\u7740\u4ec0\u4e48"},"content":{"rendered":"\n

c++ Insight<\/h2>\n\n\n\n

\u9996\u5148\uff0c\u7528c++ insight\u770b\u770bloop based loop\u8fd9\u4e2a\u8bed\u6cd5\u7cd6\u7a76\u7adf\u505a\u4e86\u4ec0\u4e48 \u200b<\/p>\n\n\n\n

\/\/original\nint func() {\n    std::map<int,int> a;\n    for(auto&& [k,v]:a){\n \u00a0 \u00a0 \u00a0int d = k+v;\n \u00a0  }\n \u00a0 \u00a0return 0;\n}\n\/\/generated by c++ insight\nint func()\n{\n \u00a0std::map<int, int, std::less<int>, std::allocator<std::pair<const int, int> > > a = std::map<int, int, std::less<int>, std::allocator<std::pair<const int, int> > >();\n  {\n \u00a0 \u00a0std::map<int, int, std::less<int>, std::allocator<std::pair<const int, int> > > & __range1 = a;\n \u00a0 \u00a0std::_Rb_tree_iterator<std::pair<const int, int> > __begin1 = __range1.begin();\n \u00a0 \u00a0std::_Rb_tree_iterator<std::pair<const int, int> > __end1 = __range1.end();\n \u00a0 \u00a0for(; !operator==(__begin1, __end1); __begin1.operator++()) {\n \u00a0 \u00a0 \u00a0std::pair<const int, int> & __operator12 = __begin1.operator*();\n \u00a0 \u00a0 \u00a0const int & k = std::get<0UL>(__operator12);\n \u00a0 \u00a0 \u00a0int & v = std::get<1UL>(__operator12);\n \u00a0 \u00a0 \u00a0int d = k + v;\n \u00a0  }\n \u00a0 \u00a0\n  }\n \u00a0return 0;\n}<\/code><\/pre>\n\n\n\n
\u53ef\u4ee5\u770b\u5230range based loop\u5728\u8bed\u6cd5\u5c42\u9762\uff0c\u5c31\u662f\u7b80\u5355\u7684\u904d\u5386\u8fed\u4ee3\u5668\u3002\u6ce8\u610f\u5176\u4e2d\u83b7\u5f97\u5143\u7d20\u4f7f\u7528\u7684\u662f__begin1.operator*()<\/code><\/p>\n\n\n\n
universal reference<\/h2>\n\n\n\n
effective modern c++\u7684item24\u662f\uff1a\u533a\u5206\u53f3\u503c\u5f15\u7528\u548c\u901a\u7528\u5f15\u7528\uff08universal reference\uff09<\/p>\n\n\n\n
\u4e00\u822c\u6765\u8bf4\uff0c\u5982\u679c\u6211\u4eec\u76f4\u63a5\u4f7f\u7528\u53d8\u91cf\u7c7b\u578b+&&\uff0c\u8fd9\u6837\u5b50\u8868\u793a\u7684\u53f3\u503c\u5f15\u7528<\/p>\n\n\n\n
\u53f3\u503c\u5f15\u7528\u53ea\u53ef\u4ee5\u7ed1\u5b9a\u53f3\u503c\uff0c\u4e0d\u53ef\u4ee5\u7ed1\u5b9a\u5de6\u503c<\/p>\n\n\n\n
\u800c\u5982\u679c\u662f\u7c7b\u4f3cT&&\u7684\u5f62\u5f0f\uff0c\u4e14T\u662f\u9700\u8981\u8fdb\u884c\u6a21\u677f\u5339\u914d\u7684\uff0c\u90a3\u4e48\u8868\u793a\u7684\u5c31\u4e0d\u662f\u53f3\u503c\u5f15\u7528\uff0c\u800c\u662f\u901a\u7528\u5f15\u7528\u3002<\/p>\n\n\n\n
\u901a\u7528\u5f15\u7528\u57fa\u672c\u4e0a\u4ec0\u4e48\u90fd\u53ef\u4ee5\u7ed1\u5b9a\uff08pretty much any\uff09\uff0c\u5de6\u503c\uff0c\u53f3\u503c\uff0cconst\uff0cvolatile\u901a\u6740\uff0c\u6240\u4ee5\u4e00\u822c\u7528\u6765\u505a\u6a21\u677f\u51fd\u6570\u91cc\u9762\u7684\u53c2\u6570\u8f6c\u53d1\u7528\u7684\u6bd4\u8f83\u591a<\/p>\n\n\n\n
\u9664\u4e86\u8f6c\u53d1\u4f1a\u7528\u5230\uff0cauto&&<\/code>\u4e5f\u662f\u4e00\u4e2a\u901a\u7528\u5f15\u7528\u3002\u901a\u7528\u5f15\u7528\u7684\u5177\u4f53\u7c7b\u578b\u53d6\u51b3\u4e8e\u7ed9\u4ed6\u521d\u59cb\u5316\u65f6\u5019\u7528\u7684\u662f\u5de6\u503c\u8fd8\u662f\u53f3\u503c\u3002<\/p>\n\n\n\n
\u901a\u8fc7c++ insight\u53ef\u4ee5\u770b\u5230\u521d\u59cb\u5316\u65f6\u901a\u8fc7__begin1.operator*()<\/code>\uff0c\u4e00\u822c\u6765\u8bf4\u662f\u5de6\u503c\u5f15\u7528\u3002<\/p>\n\n\n\n
\u56e0\u6b64\u53ea\u8981__begin1.operator*()<\/code>\u8fd4\u56de\u5de6\u503c\u5f15\u7528\uff0crange based loop\u4e2d\u4f7f\u7528auto&<\/code>\u548cauto&&<\/code>\u662f\u6ca1\u533a\u522b\u7684\uff0c\u90fd\u662f\u8868\u793a\u5de6\u503c\u5f15\u7528\u3002<\/p>\n\n\n\n
\u6211\u4e4b\u524d\u4e4b\u6240\u4ee5\u8ff7\u60d1\uff0c\u5c31\u662f\u628a\u8fd9\u91cc\u7684&&\u5f53\u4f5c\u4e86\u53f3\u503c\u5f15\u7528\u3002\u5b9e\u9645\u4e0a\u8fd9\u91cc\u662f\u901a\u7528\u5f15\u7528\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
c++ Insight \u9996\u5148\uff0c\u7528c++ insight\u770b\u770bloop based loop\u8fd9\u4e2a\u8bed\u6cd5\u7cd6\u7a76… \u7ee7\u7eed\u9605\u8bfb c++\u4e2drange based loop\u4e2d\u7684&&\u7a76\u7adf\u610f\u5473\u7740\u4ec0\u4e48<\/span><\/i><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":{"0":"post-269","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"hentry","6":"category-uncategorized","7":"h-entry","9":"h-as-article"},"_links":{"self":[{"href":"http:\/\/iamnear.top\/index.php?rest_route=\/wp\/v2\/posts\/269","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/iamnear.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/iamnear.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/iamnear.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/iamnear.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=269"}],"version-history":[{"count":2,"href":"http:\/\/iamnear.top\/index.php?rest_route=\/wp\/v2\/posts\/269\/revisions"}],"predecessor-version":[{"id":271,"href":"http:\/\/iamnear.top\/index.php?rest_route=\/wp\/v2\/posts\/269\/revisions\/271"}],"wp:attachment":[{"href":"http:\/\/iamnear.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=269"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/iamnear.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=269"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/iamnear.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=269"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}