{"id":16,"date":"2015-05-01T14:44:24","date_gmt":"2015-05-01T06:44:24","guid":{"rendered":"http:\/\/zfframework.com\/blog\/?p=16"},"modified":"2019-08-26T15:21:03","modified_gmt":"2019-08-26T07:21:03","slug":"c-%e4%bb%8e%e4%b8%80%e4%b8%aa%e7%ae%80%e5%8d%95%e7%9a%84-compare-%e8%af%b4%e5%bc%80%e5%8e%bb","status":"publish","type":"post","link":"http:\/\/zsaber.com\/blog\/p\/16","title":{"rendered":"[C++] \u4ece\u4e00\u4e2a\u7b80\u5355\u7684 compare \u8bf4\u5f00\u53bb"},"content":{"rendered":"

compare \u4ec0\u4e48\u7684\u5927\u5bb6\u90fd\u5f88\u719f\u4e86:<\/p>\n

int compare(int, int) {...}<\/code><\/pre>\n
\u60f3\u5199\u901a\u7528\u4e00\u4e9b? \u52a0\u5f3a\u7248:<\/p>\n
template<typename T>\nint compare(T const &, T const &) {...}<\/code><\/pre>\n
\u7c7b\u578b\u6cdb\u5316? \u9ed8\u8ba4\u7c7b\u578b\u53c2\u6570? … \u6700\u7ec8\u4f1a\u51fa\u73b0\u7c7b\u4f3c\u8fd9\u6837\u7684\u7248\u672c: (\u6d89\u53ca\u5230\u51fd\u6570\u5230\u5e95\u8981\u91cd\u8f7d\u8fd8\u662f\u7279\u5316, \u4ee5\u53ca\u51fd\u6570\u6a21\u677f\u4e0d\u652f\u6301\u9ed8\u8ba4\u53c2\u6570\u7b49\u95ee\u9898, \u6b64\u5904\u6682\u4e0d\u8ba8\u8bba\u8be5\u95ee\u9898)<\/p>\n
template<typename T0, typename T1>\nclass CompareHolder\n{\npublic:\n    static int compare(T0 const &, T1 const &) {...}\n};\ntemplate<typename T0, typename T1>\nint compare(T0 const &v0, T1 const &v1)\n{\n    return CompareHolder<T0, T1>::compare(v0, v1);\n}<\/code><\/pre>\n
\u597d\u4e86, \u5b66\u9662\u6d3e\u7684\u4e1c\u897f\u626f\u5b8c\u4e86, \u5f00\u59cb\u5b9e\u7528\u6d3e, \u9996\u5148\u81ea\u7136\u662f\u81ea\u5b9a\u4e49\u7c7b\u578b\u7684\u6a21\u677f\u7279\u5316:<\/p>\n
class YourType {...}\ntemplate<>\nclass CompareHolder<YourType, YourType>\n{\npublic:\n    static int compare(YourType const &, YourType const &) {...}\n};<\/code><\/pre>\n
\u4e8e\u662f\u626f\u51fa\u4e86\u672c\u6587\u7684\u91cd\u70b9: \u5f53 YourType \u6709\u4e00\u4e2a\u5b50\u7c7b, \u5e76\u4e14\u4f60\u5e0c\u671b\u4e0d\u5199\u4efb\u4f55\u4ee3\u7801, \u8ba9\u8fd9\u4e2a\u5b50\u7c7b\u4f7f\u7528\u7236\u7c7b\u7684\u7279\u5316\u7248\u672c, \u5e94\u8be5\u5982\u4f55\u505a\u5462?<\/p>\n
\u548b\u770b\u4e00\u4e0b\u5f88\u7b80\u5355\u5bf9\u5427? \u5199\u4e00\u5199\u5c31\u77e5\u9053\u4e2a\u4e2d\u86cb\u75bc\u4e4b\u5904\u4e86, \u6709\u5174\u8da3\u8bf7\u5148\u81ea\u884c\u5c1d\u8bd5\u4f53\u4f1a\u4e00\u4e0b<\/p>\n
\n
\u76f4\u63a5\u4e0a\u6700\u7ec8\u7684\u89e3\u51b3\u65b9\u6848:<\/p>\n
\u9996\u5148\u9700\u8981\u4e00\u4e2a\u4e1c\u897f, \u80fd\u591f\u5728\u7f16\u8bd1\u671f\u5224\u65ad\u67d0\u4e2a\u7c7b\u662f\u5426\u662f\u53e6\u4e00\u4e2a\u7c7b\u7684\u5b50\u7c7b<\/p>\n
template<typename TChild, typename TBase>\nclass ClassIsTypeOf\n{\nprivate:\n    class _Yes {};\n    class _No {char dummy[16];};\n    static _Yes _test(TBase *);\n    static _No _test(...);\npublic:\n    enum {value = (sizeof(_test((TChild *)0)) == sizeof(_Yes))};\n};\n#define CLASS_IS_TYPE_OF(TChild, TBase) ClassIsTypeOf<TChild, TBase>::value<\/code><\/pre>\n
\u5982\u679c TChild \u662f TBase \u7684\u5b50\u7c7b, \u5219 _test \u4f1a\u8c03\u7528\u5230 "_Yes _test(TBase *)" \u7684\u7248\u672c, \u6700\u7ec8\u5bfc\u81f4 value \u4e3a 1, \u800c\u8fd9\u4e9b\u90fd\u662f\u53ef\u4ee5\u5728\u7f16\u8bd1\u671f\u51b3\u5b9a<\/p>\n
\n
\u7136\u540e\u9700\u8981\u4e00\u4e2a\u4e1c\u897f, \u80fd\u591f\u628a 0 \u548c 1 \u53d8\u6210 "\u53ef\u63a8\u5bfc" \u4ee5\u53ca "\u4e0d\u53ef\u63a8\u5bfc" \u7684\u4e1c\u897f (STL \u4e2d\u6709\u7c7b\u4f3c\u7684\u4e1c\u897f: enable_if)<\/p>\n
template<typename T, int condition>\nclass EnableIf\n{\n};\ntemplate\nclass EnableIf<T, 1>\n{\npublic:\n    typedef void Type;\n};<\/code><\/pre>\n
\u6709\u4e86\u8fd9\u8d27, \u7531\u4e8e EnableIf<DummyType, 0>::Type \u6ca1\u6709\u5b9a\u4e49, \u5982\u679c\u5f15\u7528\u7684\u8bdd, \u7f16\u8bd1\u4e0d\u901a\u8fc7, \u53ef\u4ee5\u9020\u6210\u4f9d\u8d56\u5b83\u7684\u4e1c\u897f\u65e0\u6cd5\u6b63\u5e38\u63a8\u5bfc<\/p>\n
\n
\u63a5\u4e0b\u6765, \u6211\u4eec\u8981\u6539\u9020\u4e00\u4e0b compare, \u8ba9\u5b83\u591a\u51e0\u4e2a\u7a7a\u53c2\u6570, \u4f7f\u5f97\u4e0a\u9762\u7684 EnableIf \u80fd\u6392\u4e0a\u7528\u573a<\/p>\n
template<typename T0, typename T1, typename Fix0 = void, typename Fix1 = void>\nclass CompareHolder\n{\npublic:\n    static int compare(T0 const &, T1 const &) {...}\n};<\/code><\/pre>\n
\u8fd8\u6709\u7528\u4e8e\u52a0\u8f7d\u5b83\u7684 loader:<\/p>\n
template<typename T0, typename T1>\nint compare(T0 const &v0, T1 const &v1)\n{\n    return CompareHolder<T0, T1>::compare(v0, v1);\n}<\/code><\/pre>\n
\n
\u6700\u540e, \u628a\u6d51\u8eab\u89e3\u6570\u90fd\u5c4e\u51fa\u6765, \u5f00\u59cb\u6211\u4eec\u53c8\u81ed\u53c8\u957f\u7684\u7279\u5316\u7248\u672c: (\u8bbe\u540d\u5b57\u53eb YourType0 \u548c YourType1)<\/p>\n
template<typename T0, typename T1>\nclass CompareHolder<T0, T1\n        , typename EnableIf<YourType0, CLASS_IS_TYPE_OF(T0, YourType0)>::Type\n        , typename EnableIf<YourType1, CLASS_IS_TYPE_OF(T1, YourType1)>::Type\n    >\n{\npublic:\n    static int compare(T0 const &, T1 const &) {...}\n};<\/code><\/pre>\n
\u6655\u4e86\u6ca1? \u6655\u4e86\u5c31\u5bf9\u4e86<\/p>\n
\u8fd9\u91cc\u7279\u5316\u7684\u4e0d\u662f T0, T1, \u800c\u662f Fix0, Fix1<\/p>\n
\u5f53 T0\/T1 \u4e0d\u662f YourType0\/YourType1 \u7684\u5b50\u7c7b\u65f6, EnableIf<YourType0, CLASS_IS_TYPE_OF(T0, YourType0)>::Type<\/code> \u6700\u7ec8\u7684\u63a8\u5bfc\u7ed3\u679c\u662f\u672a\u5b9a\u4e49, \u5bfc\u81f4\u7279\u5316\u7248\u672c\u63a8\u5bfc\u5931\u8d25, \u7f16\u8bd1\u5668\u5c31\u4f1a\u81ea\u52a8\u4f7f\u7528\u975e\u7279\u5316\u7248\u672c<\/p>\n
\u53cd\u4e4b, \u867d\u7136 EnableIf \u6700\u7ec8\u7684\u63a8\u5bfc\u7ed3\u679c\u4e0e\u975e\u7279\u5316\u7248\u672c\u540c\u6837\u662f void, \u4f46\u662f\u7531\u4e8e\u5176\u6574\u4f53\u662f\u4f5c\u4e3a\u4e00\u4e2a typename, \u7f16\u8bd1\u5668\u4f1a\u5c06\u5176\u89c6\u4e3a\u4e00\u4e2a type, \u4ece\u800c\u5b83\u4f1a\u88ab\u89c6\u4e3a\u4e00\u4e2a\u63a8\u5bfc\u6210\u529f\u7684\u7279\u5316\u7248\u672c, \u6700\u7ec8\u8c03\u7528\u8be5\u7279\u5316\u7684\u7248\u672c<\/p>\n
\n
STL \u4e2d\u5e94\u8be5\u6709\u7c7b\u4f3c\u7684\u5904\u7406\u65b9\u5f0f, \u81f3\u5c11\u6709 std::enable_if, \u5177\u4f53\u7684\u6ca1\u7ec6\u770b, STL \u4ec0\u4e48\u7684\u6211\u5c31\u53ea\u7528\u7528 vector\/map \u8fde iostream \u90fd\u4e0d\u7528\u4f60\u4ee5\u4e3a\u6211\u4f1a\u4e71\u8bf4?<\/p>\n
\u53e6\u5916, \u5176\u5b9e\u53ef\u4ee5\u63d0\u4f9b\u4e00\u4e2a\u5168\u5c40\u7684 operator <, >, == \u7b49\u6bd4\u8f83\u51fd\u6570, \u4f46\u662f\u67d0\u4e9b\u60c5\u51b5\u4e0b\u8fd8\u662f\u4e0d\u65b9\u4fbf, \u800c\u901a\u8fc7\u6a21\u677f\u7279\u5316\u53ef\u4ee5\u51cf\u5c0f\u5bf9\u539f\u6709\u4ee3\u7801\u7684\u5f71\u54cd<\/p>\n
C++ \u679c\u7136\u5f88\u96be\u554a… \u4ee5\u540e\u518d\u4e5f\u4e0d\u6562\u8bf4\u7cbe\u901a C++ \u4e86<\/p>\n
over<\/p>\n","protected":false},"excerpt":{"rendered":"
compare \u4ec0\u4e48\u7684\u5927\u5bb6\u90fd\u5f88\u719f\u4e86: int compare(int, int) {…} \u60f3\u5199\u901a\u7528\u4e00\u4e9b? \u2026 Read More »<\/a><\/span><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"yoast_head":"\n[C++] \u4ece\u4e00\u4e2a\u7b80\u5355\u7684 compare \u8bf4\u5f00\u53bb - \u67d0Z\u7684\u535a\u5ba2<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"http:\/\/zsaber.com\/blog\/p\/16\" \/>\n<meta property=\"og:locale\" content=\"zh_CN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[C++] \u4ece\u4e00\u4e2a\u7b80\u5355\u7684 compare \u8bf4\u5f00\u53bb - \u67d0Z\u7684\u535a\u5ba2\" \/>\n<meta property=\"og:description\" content=\"compare \u4ec0\u4e48\u7684\u5927\u5bb6\u90fd\u5f88\u719f\u4e86: int compare(int, int) {...} \u60f3\u5199\u901a\u7528\u4e00\u4e9b? 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