{"id":2359,"date":"2018-12-06T15:43:32","date_gmt":"2018-12-06T07:43:32","guid":{"rendered":"https:\/\/damogame.cn:15443\/wordpress\/?p=2359"},"modified":"2018-12-06T15:43:32","modified_gmt":"2018-12-06T07:43:32","slug":"c%e9%ab%98%e7%ba%a7%e7%89%b9%e6%80%a7","status":"publish","type":"post","link":"https:\/\/i007.cc\/wordpress\/archives\/2359","title":{"rendered":"C++\u9ad8\u7ea7\u7279\u6027"},"content":{"rendered":"

C++\u9ad8\u7ea7\u7279\u6027<\/span><\/h1>\n

\u4e3b\u8981\u4ee5C++11\/C++14\u4e3a\u4e3b\uff0c\u6574\u7406\u4e86\u4e00\u4e0b\u6211\u5728\u65e5\u5e38\u5de5\u4f5c\u4e2d\u7ecf\u5e38\u7528\u5230\u7684\u65b0\u7279\u6027\u3002<\/p>\n

1. \u53d8\u91cf\u548c\u57fa\u672c\u7c7b\u578b<\/h2>\n

1.1 long long \u7c7b\u578b<\/h3>\n

\u6269\u5c55\u7cbe\u5ea6\u6d6e\u70b9\u6570\uff0c10\u4f4d\u6709\u6548\u6570\u5b57\u3002<\/p>\n

1.2 \u5bb9\u5668\u5217\u8868\u521d\u59cb\u5316<\/h3>\n

\u5728\u6211\u4eec\u5b9e\u9645\u7f16\u7a0b\u4e2d\uff0c\u6211\u4eec\u7ecf\u5e38\u4f1a\u78b0\u5230\u53d8\u91cf\u521d\u59cb\u5316\u7684\u95ee\u9898\uff0c\u5bf9\u4e8e\u4e0d\u540c\u7684\u53d8\u91cf\u521d\u59cb\u5316\u7684\u624b\u6bb5\u591a\u79cd\u591a\u6837\uff0c\u6bd4\u5982\u8bf4\u5bf9\u4e8e\u4e00\u4e2a\u6570\u7ec4\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528 int arr[] = {1,2,3}<\/code><\/span>\u7684\u65b9\u5f0f\u521d\u59cb\u5316\uff0c\u53c8\u6bd4\u5982\u5bf9\u4e8e\u4e00\u4e2a\u7b80\u5355\u7684\u7ed3\u6784\u4f53\uff1a<\/p>\n

struct<\/span> A<\/span><\/span>\r\n{<\/span>\r\n    int<\/span> x<\/span>;<\/span>\r\n    int<\/span> y<\/span>;<\/span>\r\n}a<\/span>=<\/span>{1<\/span>,2<\/span>};<\/span><\/pre>\n
\u8fd9\u4e9b\u4e0d\u540c\u7684\u521d\u59cb\u5316\u65b9\u6cd5\u90fd\u6709\u5404\u81ea\u7684\u9002\u7528\u8303\u56f4\u548c\u4f5c\u7528\uff0c\u4e14\u5bf9\u4e8e\u7c7b\u6765\u8bf4\u4e0d\u80fd\u7528\u8fd9\u79cd\u521d\u59cb\u5316\u7684\u65b9\u6cd5\uff0c\u6700\u4e3b\u8981\u7684\u662f\u6ca1\u6709\u4e00\u79cd\u53ef\u4ee5\u901a\u7528\u7684\u521d\u59cb\u5316\u65b9\u6cd5\u9002\u7528\u6240\u6709\u7684\u573a\u666f\uff0c\u56e0\u6b64C++11\u4e2d\u4e3a\u4e86\u7edf\u4e00\u521d\u59cb\u5316\u65b9\u5f0f\uff0c\u63d0\u51fa\u4e86\u5217\u8868\u521d\u59cb\u5316\uff08list-initialization\uff09\u7684\u6982\u5ff5\u3002<\/p>\n
\u5728C++98\/03\u4e2d\u6211\u4eec\u53ea\u80fd\u5bf9\u666e\u901a\u6570\u7ec4\u548cPOD(plain old data\uff0c\u7b80\u5355\u6765\u8bf4\u5c31\u662f\u53ef\u4ee5\u7528memcpy\u590d\u5236\u7684\u5bf9\u8c61)\u7c7b\u578b\u53ef\u4ee5\u4f7f\u7528\u5217\u8868\u521d\u59cb\u5316\uff0c\u5728C++11\u4e2d\u521d\u59cb\u5316\u5217\u8868\u88ab\u9002\u7528\u6027\u88ab\u653e\u5927\uff0c\u53ef\u4ee5\u4f5c\u7528\u4e8e\u4efb\u4f55\u7c7b\u578b\u5bf9\u8c61\u7684\u521d\u59cb\u5316\u3002\u5982\u4e0b\uff1a<\/p>\n
class<\/span> Foo<\/span><\/span>\r\n{<\/span>\r\npublic<\/span>:<\/span>\r\n    Foo<\/span>(int<\/span>) {}<\/span>\r\nprivate<\/span>:<\/span>\r\n    Foo<\/span>(const<\/span> Foo<\/span> &<\/span>);<\/span>\r\n};<\/span>\r\n \r\nint<\/span> _tmain<\/span>(int<\/span> argc<\/span>, _TCHAR<\/span>*<\/span> argv<\/span>[])<\/span>\r\n{<\/span>\r\n    Foo<\/span> a1<\/span>(123<\/span>); \/\/\u8c03\u7528Foo(int)\u6784\u9020\u51fd\u6570\u521d\u59cb\u5316<\/span><\/span>\r\n    Foo<\/span> a2<\/span> =<\/span> 123<\/span>; \/\/error Foo\u7684\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u58f0\u660e\u4e3a\u79c1\u6709\u7684\uff0c\u8be5\u5904\u7684\u521d\u59cb\u5316\u65b9\u5f0f\u662f\u9690\u5f0f\u8c03\u7528Foo(int)\u6784\u9020\u51fd\u6570\u751f\u6210\u4e00\u4e2a\u4e34\u65f6\u7684\u533f\u540d\u5bf9\u8c61\uff0c\u518d\u8c03\u7528\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u5b8c\u6210\u521d\u59cb\u5316<\/span><\/span>\r\n \r\n    Foo<\/span> a3<\/span> =<\/span> { 123<\/span> }; \/\/\u5217\u8868\u521d\u59cb\u5316<\/span><\/span>\r\n    Foo<\/span> a4<\/span> { 123<\/span> }; \/\/\u5217\u8868\u521d\u59cb\u5316<\/span><\/span>\r\n \r\n    int<\/span> a5<\/span> =<\/span> { 3<\/span> };<\/span>\r\n    int<\/span> a6<\/span> { 3<\/span> };<\/span>\r\n    return<\/span> 0<\/span>;<\/span>\r\n}<\/span><\/pre>\n
\u7531\u4e0a\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u53ef\u4ee5\u770b\u51fa\uff0c\u5728C++11\u4e2d\uff0c\u5217\u8868\u521d\u59cb\u5316\u4e0d\u4ec5\u80fd\u5b8c\u6210\u5bf9\u666e\u901a\u7c7b\u578b\u7684\u521d\u59cb\u5316\uff0c\u8fd8\u80fd\u5b8c\u6210\u5bf9\u7c7b\u7684\u5217\u8868\u521d\u59cb\u5316\uff0c\u9700\u8981\u6ce8\u610f\u7684\u662fa3\u3001a4\u90fd\u662f\u5217\u8868\u521d\u59cb\u5316\uff0c\u79c1\u6709\u7684\u62f7\u8d1d\u5e76\u4e0d\u5f71\u54cd\u5b83\uff0c\u4ec5\u8c03\u7528\u7c7b\u7684\u6784\u9020\u51fd\u6570\u800c\u4e0d\u9700\u8981\u62f7\u8d1d\u6784\u9020\u51fd\u6570\uff0ca4\u3001a6\u7684\u5199\u6cd5\u662fC++98\/03\u6240\u4e0d\u5177\u5907\u7684\uff0c\u662fC++11\u65b0\u589e\u7684\u5199\u6cd5\u3002<\/p>\n
\u540c\u65f6\u5217\u8868\u521d\u59cb\u5316\u65b9\u6cd5\u4e5f\u9002\u7528\u4e8e\u7528new\u64cd\u4f5c\u7b49\u5706\u62ec\u53f7\u8fdb\u884c\u521d\u59cb\u5316\u7684\u5730\u65b9\uff0c\u5982\u4e0b\uff1a<\/p>\n
int*<\/span> a<\/span> =<\/span> new<\/span> int<\/span> { 3<\/span> };<\/span>\r\ndouble<\/span> b<\/span> =<\/span> double<\/span>{ 12.12<\/span> };<\/span>\r\nint<\/span> *<\/span> arr<\/span> =<\/span> new<\/span> int<\/span>[] {1<\/span>, 2<\/span>, 3<\/span>};<\/span><\/pre>\n
\u5728C++11\u4e2d\u53ef\u4ee5\u4f7f\u7528\u5217\u8868\u521d\u59cb\u5316\u65b9\u6cd5\u5bf9\u5806\u4e2d\u5206\u914d\u7684\u5185\u5b58\u7684\u6570\u7ec4\u8fdb\u884c\u521d\u59cb\u5316\uff0c\u800c\u5728C++98\/03\u4e2d\u662f\u4e0d\u80fd\u8fd9\u6837\u505a\u7684\u3002\u6b64\u5916\uff0c\u8fd8\u6709\u4e00\u4e9b\u7ec6\u8282\u9700\u8981\u6ce8\u610f\uff1a<\/p>\n
struct<\/span> A<\/span><\/span>\r\n{<\/span>\r\n    int<\/span> x<\/span>;<\/span>\r\n    int<\/span> y<\/span>;<\/span>\r\n}a<\/span> =<\/span> {123<\/span>, 321<\/span>};<\/span>\r\n \/\/a.x = 123 a.y = 321<\/span><\/span>\r\n \r\nstruct<\/span> B<\/span><\/span>\r\n{<\/span>\r\n    int<\/span> x<\/span>;<\/span>\r\n    int<\/span> y<\/span>;<\/span>\r\n    B<\/span>(int<\/span>, int<\/span>) :x<\/span>(0<\/span>), y<\/span>(0<\/span>){}<\/span>\r\n}b<\/span> =<\/span> {123<\/span>,321<\/span>};<\/span>\r\n\/\/b.x = 0  b.y = 0<\/span><\/span><\/pre>\n
\u5bf9\u4e8e\u81ea\u5b9a\u4e49\u7684\u7ed3\u6784\u4f53A\u6765\u8bf4\u6a21\u5f0f\u666e\u901a\u7684POD\u7c7b\u578b\uff0c\u4f7f\u7528\u5217\u8868\u521d\u59cb\u5316\u5e76\u4e0d\u4f1a\u5f15\u8d77\u95ee\u9898\uff0cx,y\u90fd\u88ab\u6b63\u786e\u7684\u521d\u59cb\u5316\u4e86\uff0c\u4f46\u770b\u4e0b\u7ed3\u6784\u4f53B\u548c\u7ed3\u6784\u4f53A\u7684\u533a\u522b\u5728\u4e8e\u7ed3\u6784\u4f53B\u5b9a\u4e49\u4e86\u4e00\u4e2a\u6784\u9020\u51fd\u6570\uff0c\u5e76\u4f7f\u7528\u4e86\u6210\u5458\u521d\u59cb\u5316\u5217\u8868\u6765\u521d\u59cb\u5316B\u7684\u4e24\u4e2a\u53d8\u91cf\uff0c\u56e0\u6b64\u5217\u8868\u521d\u59cb\u5316\u5728\u8fd9\u91cc\u5c31\u4e0d\u8d77\u4f5c\u7528\u4e86\uff0cb\u91c7\u7528\u7684\u662f\u6784\u9020\u51fd\u6570\u7684\u65b9\u5f0f\u6765\u5b8c\u6210\u53d8\u91cf\u7684\u521d\u59cb\u5316\u5de5\u4f5c\u3002<\/p>\n
C++11\u7684\u5217\u8868\u521d\u59cb\u5316\u8fd8\u6709\u4e00\u4e2a\u989d\u5916\u7684\u529f\u80fd\u5c31\u662f\u53ef\u4ee5\u9632\u6b62\u7c7b\u578b\u6536\u7a84\uff0c\u4e5f\u5c31\u662fC++98\/03\u4e2d\u7684\u9690\u5f0f\u7c7b\u578b\u8f6c\u6362\uff0c\u5c06\u8303\u56f4\u5927\u7684\u8f6c\u6362\u4e3a\u8303\u56f4\u5c0f\u7684\u8868\u793a\uff0c\u5728C++98\/03\u4e2d\u7c7b\u578b\u6536\u7a84\u5e76\u4e0d\u4f1a\u7f16\u8bd1\u51fa\u9519\uff0c\u800c\u5728C++11\u4e2d\uff0c\u4f7f\u7528\u5217\u8868\u521d\u59cb\u5316\u7684\u7c7b\u578b\u6536\u7a84\u7f16\u8bd1\u5c06\u4f1a\u62a5\u9519\uff1a<\/p>\n
int<\/span> a<\/span> =<\/span> 1.1<\/span>; \/\/OK<\/span><\/span>\r\nint<\/span> b<\/span>{ 1.1<\/span> }; \/\/error<\/span><\/span>\r\n \r\nfloat<\/span> f1<\/span> =<\/span> 1e40<\/span>; \/\/OK<\/span><\/span>\r\nfloat<\/span> f2<\/span>{ 1e40<\/span> }; \/\/error<\/span><\/span>\r\n \r\nconst<\/span> int<\/span> x<\/span> =<\/span> 1024<\/span>, y<\/span> =<\/span> 1<\/span>;<\/span>\r\nchar<\/span> c<\/span> =<\/span> x<\/span>; \/\/OK<\/span><\/span>\r\nchar<\/span> d<\/span>{ x<\/span> };\/\/error<\/span><\/span>\r\nchar<\/span> e<\/span> =<\/span> y<\/span>;\/\/error<\/span><\/span>\r\nchar<\/span> f<\/span>{ y<\/span> };\/\/error<\/span><\/span><\/pre>\n
\u4e0a\u9762\u4f8b\u5b50\u770b\u51fa\uff0c\u7528C++98\/03\u7684\u65b9\u5f0f\u7c7b\u578b\u6536\u7a84\u5e76\u4e0d\u4f1a\u7f16\u8bd1\u62a5\u9519\uff0c\u4f46\u662f\u5c06\u4f1a\u5bfc\u81f4\u4e00\u4e9b\u9690\u85cf\u7684\u9519\u8bef\uff0c\u5bfc\u81f4\u51fa\u9519\u7684\u65f6\u5019\u5f88\u96be\u5b9a\u4f4d\uff0c\u800c\u5229\u7528C++11\u7684\u5217\u8868\u521d\u59cb\u5316\u65b9\u6cd5\u5b9a\u4e49\u53d8\u91cf\u4ece\u6e90\u5934\u4e86\u904f\u5236\u4e86\u7c7b\u578b\u6536\u7a84\uff0c\u4f7f\u5f97\u4e0d\u6070\u5f53\u7684\u7528\u6cd5\u5c31\u4e0d\u4f1a\u7528\u5728\u7a0b\u5e8f\u4e2d\uff0c\u907f\u514d\u4e86\u67d0\u4e9b\u4f4d\u7f6e\u7c7b\u578b\u7684\u9519\u8bef\uff0c\u56e0\u6b64\u5efa\u8bae\u4ee5\u540e\u5728\u5b9e\u9645\u7f16\u7a0b\u4e2d\u5c3d\u53ef\u80fd\u7684\u4f7f\u7528\u5217\u8868\u521d\u59cb\u5316\u65b9\u6cd5\u5b9a\u4e49\u53d8\u91cf\u3002<\/p>\n
1.3 nullptr\u5e38\u91cf<\/h3>\n
C++11\u4e2d\u65b0\u589enullptr<\/code><\/span>\u5e38\u91cf\uff0c\u7528\u4e8e\u751f\u6210\u7a7a\u6307\u9488\uff0c\u4ee3\u66ff\u4e4b\u524d\u4f7f\u7528\u7684NULL<\/code><\/span>\u548c0\u3002\u76ee\u524d\u67093\u79cd\u521d\u59cb\u5316\u7a7a\u6307\u9488\u7684\u65b9\u6cd5\uff1a<\/p>\n
int<\/span> *<\/span>p1<\/span> =<\/span> nullptr<\/span>; <\/span>\r\nint<\/span> *<\/span>p2<\/span> =<\/span> 0<\/span>;<\/span>\r\nint<\/span> *<\/span>p3<\/span> =<\/span> NULL<\/span>; <\/span><\/pre>\n
\u4f7f\u7528 nullptr<\/code><\/span> \u4ee3\u66ff 0 \u6216 NULL<\/code><\/span>\uff0c\u80fd\u663e\u8457\u63d0\u9ad8\u4ee3\u7801\u7684\u6e05\u6670\u5ea6\uff0c\u5c24\u5176\u662f\u548c auto<\/code><\/span> \u8fde\u7528\u65f6\uff1b\u8fd8\u53ef\u4ee5\u907f\u514d\u91cd\u8f7d\u51fd\u6570\u8c03\u7528\u6a21\u7cca\u7684\u95ee\u9898\u3002\u5c24\u5176\u662f\u5728\u4f7f\u7528\u6a21\u677f\u51fd\u6570\u65f6\uff0c\u4f20\u51650\u4f1a\u88ab\u63a8\u65ad\u4e3aint<\/code><\/span>\u578b\uff0c\u4e0e\u6307\u9488\u7c7b\u578b\u4e0d\u5339\u914d\u4f1a\u76f4\u63a5\u62a5\u9519\u3002<\/p>\n
1.4 constexpr\u53d8\u91cf<\/h3>\n
\u5c06\u53d8\u91cf\u58f0\u660e\u4e3aconstexpr<\/code><\/span>\u7c7b\u578b\u4ee5\u4fbf\u7531\u7f16\u8bd1\u5668\u6765\u9a8c\u8bc1\u53d8\u91cf\u7684\u503c\u662f\u5426\u662f\u4e00\u4e2a\u5e38\u91cf\u8868\u8fbe\u5f0f\uff1b\u58f0\u660e\u4e3aconstexpr<\/code><\/span>\u7684\u53d8\u91cf\u4e00\u5b9a\u662f\u4e00\u4e2a\u5e38\u91cf\uff0c\u800c\u4e14\u5fc5\u987b\u7528\u5e38\u91cf\u8868\u8fbe\u5f0f\u6765\u521d\u59cb\u5316\uff0c\u6bd4\u5982\u8bf4\u4e0b\u9762\u7684\u60c5\u51b5\u5219\u662f\u4e0d\u6b63\u786e\u7684\uff1a<\/p>\n
int<\/span> t<\/span> =<\/span> 10<\/span>;<\/span>\r\nconstexpr<\/span> int<\/span> q<\/span> =<\/span> t<\/span> +<\/span> 20<\/span>; \u00a0\/\/t\u4e0d\u662f\u5e38\u91cf\uff0c\u62a5\u9519<\/span><\/span>\r\ncout<\/span> <<<\/span> \"q\"<\/span> <<<\/span> q<\/span> <<<\/span> endl<\/span>;<\/span><\/pre>\n
\u9700\u8981\u5c06t\u58f0\u660e\u4e3a const<\/code><\/span> \u624d\u662f\u6b63\u786e\u7684\u3002\u4e00\u822c\u6765\u8bf4\uff0c\u5982\u679c\u4f60\u8ba4\u5b9a\u53d8\u91cf\u662f\u4e00\u4e2a\u5e38\u91cf\u8868\u8fbe\u5f0f\uff0c\u90a3\u5c31\u628a\u5b83\u58f0\u660e\u4e3aconstexpr<\/code><\/span>\u7c7b\u578b\uff1b<\/p>\n
constexpr<\/code><\/span>\u4e5f\u53ef\u4ee5\u7528\u4e8e\u5c06\u51fd\u6570\u58f0\u660e\u4e3a\u5e38\u91cf\u51fd\u6570\uff0c\u9700\u8981\u9075\u4ece\u51e0\u9879\u7ea6\u5b9a\uff1a<\/p>\n