{"id":595,"date":"2015-11-22T18:24:47","date_gmt":"2015-11-22T10:24:47","guid":{"rendered":"http:\/\/yangwang.hk\/?p=595"},"modified":"2016-01-01T13:56:57","modified_gmt":"2016-01-01T05:56:57","slug":"%e5%b2%94%e8%b7%af%e5%8f%a3%e3%80%81%e8%87%aa%e5%a2%9e%e4%b8%8e%e8%87%aa%e5%87%8f","status":"publish","type":"post","link":"https:\/\/yangwang.hk\/?p=595","title":{"rendered":"\u5c94\u8def\u53e3\u3001\u81ea\u589e\u4e0e\u81ea\u51cf"},"content":{"rendered":"<p>\u5728\u524d\u9762\u7684\u5faa\u73af\u4e2d\uff0c\u6211\u4eec\u5df2\u7ecf\u7b80\u5355\u7684\u4ecb\u7ecd\u4e86\u81ea\u589e\u548c\u81ea\u51cf\uff0c\u6211\u4eec\u4eca\u5929\u5c31\u6765\u6b63\u5f0f\u7684\u8c08\u8c08\u8fd9\u79cd\u5199\u6cd5<\/p>\n<p>\u5f88\u591a\u65f6\u5019\uff0c\u6211\u4eec\u9700\u8981\u4e3a\u67d0\u4e00\u4e2a\u53d8\u91cf\u589e\u52a01\uff0c\u6216\u662f\u51cf\u5c111<\/p>\n<p>\u7279\u522b\u662f\u5728\u5faa\u73af\u4e2d\u3002<\/p>\n<p>\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u5e38\u89c4\u7684\u8fd0\u7b97<\/p>\n<p>\u5047\u8bbe\uff1a<strong><em>int foo = 0;<\/em><\/strong><\/p>\n<p>\u8981\u4f7f\u5f97\u6b64\u53d8\u91cf\u589e\u52a01\uff0c\u6211\u4eec\u53ef\u4ee5\u5199\u4e3afoo = foo + 1;<\/p>\n<p>\u81ea\u51cf\u5219\u53ef\u5199\u6210foo = foo &#8211; 1;<\/p>\n<p>\u5bf9\u4e8e\u8fd9\u79cd\u5bf9\u53d8\u91cf\u81ea\u8eab\u8fdb\u884c\u52a0\u51cf\u7684\uff0c\u53ef\u4ee5\u4f7f\u7528+=\u548c-=\u6765\u4ee3\u66ff<\/p>\n<p>foo += 1;<\/p>\n<p>foo -=1;<\/p>\n<p>\u524d\u540e\u4e24\u79cd\u5199\u6cd5\u662f\u7b49\u4ef7\u7684\uff0c\u4e0d\u8fc7\u503c\u5f97\u6ce8\u610f\u7684\u662f\uff0c\u5c3d\u7ba1\u4e24\u79cd\u5199\u6cd5\u7684\u7ed3\u679c\u76f8\u540c\uff0c\u4f46\u662f+=\u548c-=\u662f\u4e24\u4e2a\u5355\u72ec\u7684\u8fd0\u7b97\u7b26\uff01\u5b83\u4eec\u4e0d\u662f\u4e0a\u8ff0\u8fd0\u7b97\u7684\u7b80\u5199\uff01<\/p>\n<p>C\u8bed\u8a00\u63d0\u4f9b\u4e86\u524d\u7f00\u548c\u540e\u7f00\u7684\u81ea\u589e\u548c\u81ea\u51cf\u8fd0\u7b97\u7b26\uff0c\u5373++\u548c&#8211;<\/p>\n<p>\u8fd9\u4e24\u4e2a\u64cd\u4f5c\u7b26\u90fd\u662f\u5355\u76ee\u64cd\u4f5c\u7b26\uff0c\u5b83\u4eec\u7684\u64cd\u4f5c\u5bf9\u8c61\u5fc5\u987b\u662f\u4e00\u4e2a\u53ef\u4ee5\u4fee\u6539\u7684\u5de6\u503c\uff08\u4f8b\u5982\u53d8\u91cf\uff09<\/p>\n<p>\u663e\u7136(foo+1)++\u8fd9\u6837\u7684\u64cd\u4f5c\u662f\u4e0d\u5408\u6cd5\u7684<\/p>\n<p>&nbsp;<\/p>\n<p>foo += 1\u548c++foo\u7684\u6548\u679c\u662f\u76f8\u540c\u7684<\/p>\n<p>\u540c\u7406\uff0cfoo -= 1\u4e0e&#8211;foo\u6548\u679c\u76f8\u540c<\/p>\n<p>\u524d\u4e24\u79cd\u5199\u6cd5\u4e0d\u518d\u505a\u8ba8\u8bba\uff0c\u6211\u4eec\u5148\u4ece\u81ea\u589e\u5f00\u59cb<\/p>\n<p>\u524d\u9762\u5df2\u7ecf\u8bf4\u9053\u8fc7\uff0c\u81ea\u589e\u64cd\u4f5c\u5206\u4e3a\u524d\u7f00\u548c\u540e\u7f00\u4e24\u79cd\uff0c\u800c\u5b83\u4eec\u662f\u6709\u533a\u522b\u7684\uff0c\u6211\u4eec\u4e0b\u9762\u5c31\u7528\u7a0b\u5e8f\u6765\u5c55\u73b0\u8fd9\u4e00\u533a\u522b<\/p>\n<pre class=\"brush: cpp; title: ; notranslate\" title=\"\">\r\n#include &lt;stdio.h&gt;\r\n\r\nint main(void)\r\n{\r\n\tint foo = 1;\r\n\t\r\n\r\n\tprintf(&quot;%d\\n&quot;, foo);\r\n\tprintf(&quot;%d\\n&quot;, foo++);\r\n\tprintf(&quot;%d\\n&quot;, foo);\r\n\r\n\r\n\treturn 0;\r\n}\r\n<\/pre>\n<p>\u7f16\u8bd1\u5e76\u6267\u884c\u6b64\u4ee3\u7801\u540e\uff0c\u663e\u793a\u5982\u4e0b\uff08\u5207\u8bb0\uff0c\u4e0d\u8981\u968f\u610f\u5220\u9664\u6216\u8c03\u6574printf\u7684\u7ed3\u6784\uff0c\u539f\u56e0\u7a0d\u540e\u8c08\u5230\uff09<\/p>\n<div id=\"attachment_596\" style=\"width: 384px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/yangwang.hk\/wp-content\/uploads\/2015\/11\/test1.jpg\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-596\" class=\"size-full wp-image-596\" src=\"http:\/\/yangwang.hk\/wp-content\/uploads\/2015\/11\/test1.jpg\" alt=\"\u6d4b\u8bd5\u7ed3\u679c\" width=\"374\" height=\"85\" \/><\/a><p id=\"caption-attachment-596\" class=\"wp-caption-text\">\u6d4b\u8bd51<\/p><\/div>\n<p>\u7b2c\u4e00\u4e2aprintf\u663e\u793a\u7684\u662ffoo\u7684\u521d\u59cb\u5316\u7ed3\u679c\u3002\u6211\u4eec\u5728\u7b2c\u4e8c\u4e2aprintf\u4e2d\u4f7f\u7528\u540e\u7f00\u81ea\u589e\uff0c\u800cprintf\u8f93\u51fa\u7684\u503c\u5374\u4ecd\u7136\u4e3a1<\/p>\n<p>\u76f4\u5230\u7b2c\u4e09\u4e2aprintf\u6211\u4eec\u624d\u53d1\u73b0foo\u7684\u503c\u53d1\u751f\u4e86\u6539\u53d8<\/p>\n<p>\u8fd9\u8bf4\u660e\u5bf9\u4e8e\u540e\u7f00\u81ea\u589e\u6765\u8bf4\uff0c\u5b83\u5e76\u4e0d\u4f1a\u7acb\u5373\u6539\u53d8\u64cd\u4f5c\u7684\u53d8\u91cf\u7684\u503c\uff0c\u800c\u662f\u7b49\u5230\u4e0b\u4e00\u4e2a\u64cd\u4f5c\u5b8c\u6210\u540e\u624d\u5c06\u5176\u81ea\u589e+1<\/p>\n<p>\u8fd9\u4e00\u70b9\u548c\u4f7f\u7528i+=1\u662f\u4e0d\u4e00\u6837\u7684\uff0c\u5982\u4e0b\u56fe<br \/>\n<div id=\"attachment_598\" style=\"width: 644px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/yangwang.hk\/wp-content\/uploads\/2015\/11\/test2.jpg\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-598\" class=\"size-full wp-image-598\" src=\"http:\/\/yangwang.hk\/wp-content\/uploads\/2015\/11\/test2.jpg\" alt=\"\u6d4b\u8bd52\" width=\"634\" height=\"365\" \/><\/a><p id=\"caption-attachment-598\" class=\"wp-caption-text\">\u6d4b\u8bd52<\/p><\/div><br \/>\n\u5bf9\u4e8e\u540e\u7f00\u81ea\u51cf\u5462\uff1f\u8bf7\u81ea\u884c\u4fee\u6539\u4e0a\u9762\u7684\u4ee3\u7801\u5e76\u5c1d\u8bd5\uff08\u540c\u6837\uff0c\u4e0d\u8981\u56e0\u4e3a\u5077\u61d2\u628a\u4e09\u4e2aprintf\u5199\u4e3a\u4e00\u4e2a\uff09<\/p>\n<p>\u5bf9\u4e8e\u524d\u7f00\u81ea\u589e\uff08\u8bf7\u5c06\u7b2c\u4e5d\u884c\u66ff\u6362\u4e3a <em><strong>printf(&#8220;%d\\n&#8221;, ++foo);<\/strong><\/em> \uff09<\/p>\n<p>\u4f60\u5c06\u5f97\u5230\u548c\u7b2c\u4e8c\u6b21\u8bd5\u9a8c\u76f8\u540c\u7684\u7ed3\u679c<\/p>\n<p>\u8fd9\u8bf4\u660e\u524d\u7f00\u81ea\u589e\u4f1a\u7acb\u5373\u5c06\u53d8\u91cf\u7684\u503c+1\uff0c\u5176\u6548\u679c\u7c7b\u4f3c\u4e0efoo += 1<\/p>\n<p>\u90a3\u4e48\u5bf9\u4e8e\u4e0b\u9762\u8fd9\u4e2a\u7a0b\u5e8f<\/p>\n<pre class=\"brush: cpp; title: ; notranslate\" title=\"\">\r\n#include &lt;stdio.h&gt;\r\n\r\nint main(void)\r\n{\r\n\tint foo = 0;\r\n\tint bar = 0;\r\n\r\n\tbar = foo++ +1;\r\n\r\n\tprintf(&quot;%d&quot;, bar);\r\n\r\n\treturn 0;\r\n}\r\n<\/pre>\n<p>\u8fd0\u884c\u540e\u4f1a\u5f97\u5230\u4ec0\u4e48\u7ed3\u679c\uff1f<\/p>\n<p>&nbsp;<\/p>\n<p>\u7b54\u6848\u662f\u6bd41\u59271\u7684\u6570<\/p>\n<p>\u56e0\u4e3a\u4f7f\u7528\u540e\u7f00\u81ea\u589e\uff0c\u6240\u4ee5foo\u7684\u503c\u4e0d\u4f1a\u7acb\u5373\u6539\u53d8\uff0c\u4e8e\u662f\u4e0a\u9762\u7a0b\u5e8f\u5c31\u53d8\u6210\u4e86<\/p>\n<p><strong><em>bar = 0 + 1<\/em><\/strong><\/p>\n<p><strong><em>foo = foo + 1<\/em><\/strong><\/p>\n<p>\u4f60\u53ef\u4ee5\u5c06\u540e\u7f00\u6539\u4e3a\u524d\u7f00\uff0c\u518d\u770b\u4f1a\u6709\u4ec0\u4e48\u53d8\u5316<\/p>\n<p>&nbsp;<\/p>\n<p>\u5982\u679c\u4f60\u641e\u5b9a\u4e86\u4e0a\u9762\u4e00\u4e2a\uff0c\u8bf7\u770b\u4e0b\u9762\u7684\u8868\u8fbe\u5f0f<\/p>\n<p>(foo++)+(++foo)+(foo++)<\/p>\n<p>foo\u7684\u521d\u59cb\u503c\u4e3a0\uff0c\u8bf7\u95ee\u8fd0\u884c\u540e\u8868\u8fbe\u5f0f\u7684\u503c\u4e3a\u591a\u5c11\uff1f<\/p>\n<p>\u8fd9\u662f\u56fd\u5185\u8bb8\u591a\u6559\u6750\u91cc\u7684\u5185\u5bb9\uff0c\u800c\u4e14\u8003\u8bd5\u4e2d\u8fd8\u4f1a\u9047\u5230\u5982\u6b64\u7684\u9898\u76ee\u3002<\/p>\n<p>\u90a3\u4e48\u8fd9\u6837\u7684\u5f0f\u5b50\u5230\u5e95\u5e94\u8be5\u600e\u4e48\u8ba1\u7b97\u5462\uff1f<\/p>\n<p>\u7b54\u6848\u662f\uff1a<strong><span style=\"color: #ff0000;\">\u4e0d\u77e5\u9053<\/span><\/strong><\/p>\n<p>\u8fd9\u4e2a\u8868\u8fbe\u5f0f\u7684\u503c\u662f\u4e0d\u786e\u5b9a\u7684\uff0c\u5728\u4e0d\u540c\u7f16\u8bd1\u5668\u4e0a\uff0c\u751a\u81f3\u662f\u5728\u540c\u4e00\u4e2a\u7f16\u8bd1\u5668\u4e0a\u4f7f\u7528\u4e0d\u540c\u7684\u65b9\u5f0f\u7f16\u8bd1<\/p>\n<p>\u5f97\u5230\u7684\u7ed3\u679c\u53ef\u80fd\u90fd\u662f\u4e0d\u4e00\u6837\u7684\uff01<\/p>\n<p>\u8fd9\u79cd\u884c\u4e3a\u79f0\u4e3aUB\uff08undefine behavior\uff09,\u672a\u5b9a\u4e49\u884c\u4e3a\uff0c\u5bf9\u4e8e\u8fd9\u4e2a\u6982\u5ff5\uff0c\u6211\u4eec\u5c06\u5728\u540e\u9762\u8bb2\u5230<\/p>\n<p><span style=\"color: #ff0000;\">\u5207\u8bb0\uff0c\u4f60<strong>\u4e0d\u5e94\u8be5<\/strong>\u5728\u4e00\u4e2a\u8868\u8fbe\u5f0f\u5185\u591a\u6b21\u4f7f\u7528\u81ea\u589e\uff0c\u81ea\u51cf\u64cd\u4f5c\uff01<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5728\u524d\u9762\u7684\u5faa\u73af\u4e2d\uff0c\u6211\u4eec\u5df2\u7ecf\u7b80\u5355\u7684\u4ecb\u7ecd\u4e86\u81ea\u589e\u548c\u81ea\u51cf\uff0c\u6211\u4eec\u4eca\u5929\u5c31\u6765\u6b63\u5f0f\u7684\u8c08\u8c08\u8fd9\u79cd\u5199\u6cd5 \u5f88\u591a\u65f6\u5019\uff0c\u6211\u4eec\u9700\u8981\u4e3a\u67d0\u4e00\u4e2a\u53d8\u91cf\u2026 <span class=\"read-more\"><a href=\"https:\/\/yangwang.hk\/?p=595\">Read More: \u5c94\u8def\u53e3\u3001\u81ea\u589e\u4e0e\u81ea\u51cf &raquo;<\/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":[],"class_list":["post-595","post","type-post","status-publish","format-standard","hentry","category-c"],"views":2429,"_links":{"self":[{"href":"https:\/\/yangwang.hk\/index.php?rest_route=\/wp\/v2\/posts\/595","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/yangwang.hk\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/yangwang.hk\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/yangwang.hk\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/yangwang.hk\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=595"}],"version-history":[{"count":3,"href":"https:\/\/yangwang.hk\/index.php?rest_route=\/wp\/v2\/posts\/595\/revisions"}],"predecessor-version":[{"id":650,"href":"https:\/\/yangwang.hk\/index.php?rest_route=\/wp\/v2\/posts\/595\/revisions\/650"}],"wp:attachment":[{"href":"https:\/\/yangwang.hk\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=595"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/yangwang.hk\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=595"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/yangwang.hk\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=595"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}