C++发展简史
1998年，C++标准委员会成立，第一版ISO/IEC 14882:1998公开，即C++98。
2003年，C++标准委员会通过第二版标准ISO/IEC 14882:2003，简称C++03。
2011年，很多年的发展终于通过C++11，ISO/IEC 14882:2011，别名C++0x。
2014年，C++标准委员会一致通过C++14。ISO/IEC 14882:2014，别名C++1y。
2017年，C++又一次重大更新，官方名称 ISO/IEC 14882:2017, 别名C++1z。
2020年9月4日，C++20的国际标准草案投票结束，年底正式发布,别名C++2a。
C++ 有这么多的版本，可是对像我一样的广大初学者来说，可能C++11都还没有普及了。最近我正在学用的正则表达式正是从C++11开始支持的，头文件 <regex>，不再是只能用第三方 "boost/regex.hpp" 等等的库了。而我用的编译器是 TDM-GCC 4.9.2 64-bit，需要在菜单命令：“工具--编译选项--编译器”中设置配置，编译时加入以下命令文本框里添加 “-std=c++11”，如下图所示：
刚接触正则表达式，初步学了点皮毛记录一下。直接上代码：
#include <iostream> #include <string> #include <vector> #include <regex> using namespace std; int regexSplit(string&,const string,vector<string>&,int); int main(void) { vector <string> vect; string str = "(12.3e+10-0.018e-5)+(11.006-7.)+.89"; string reg[11]={ "(\\d+)", /*整数，包括0开头的 */ "([1-9]\\d*)", /*错：整数，但取不到0 */ "(0|[1-9]\\d*)", /*全部整数 */ "(\\d+\\.\\d+)", /*小数不包括整数 */ "(\\d*\\.?\\d+)", /*错：整数或小数，但包括7. */ "(\\d+\\.?\\d*)", /*错：整数或小数，但包括.89 */ "(\\d+|\\d+\\.\\d+)", /*整数或小数 */ "-?(\\d+|\\d+\\.\\d+)", /*正数或负数 */ "\\([^()]*\\)", /*匹配成对的括号 */ "-?(\\d+\\.\\d+)e[+-]\\d+", /*科学记数法 */ "-?((\\d+|\\d+\\.\\d+)|(\\d+\\.\\d+)e[+-]\\d+)" /*实数 */ }; cout<<str<<endl<<"--------------"<<endl; for (auto a:reg){ regexSplit(str,a,vect,0); cout<<"pattern:"<<a<<endl<<"string: "; for(auto v:vect) cout<<v<<" "; vect.clear(); //重要，否则后一次的循环取到的值会累积到vect中。 cout<<endl<<"=============="<<endl; } return 0; } int regexSplit(string &str,const string str_reg,vector<string>&vect,int pos) { if (pos!=-1) pos=0; //pos=0 匹配到的位置，pos=-1匹配位置的前一字串 regex Pattern(str_reg); sregex_token_iterator it(str.begin(),str.end(),Pattern, pos); sregex_token_iterator end; for(;it!=end;++it,i++) vect.push_back(*it); return vect.size(); //if 0 没有匹配到，else 匹配到的个数 }
输出结果：
(12.3e+10-0.018e-5)+(11.006-7.)+.89 -------------- pattern:(\d+) string: 12 3 10 0 018 5 11 006 7 89 ============== pattern:([1-9]\d*) string: 12 3 10 18 5 11 6 7 89 ============== pattern:(0|[1-9]\d*) string: 12 3 10 0 0 18 5 11 0 0 6 7 89 ============== pattern:(\d+\.\d+) string: 12.3 0.018 11.006 ============== pattern:(\d*\.?\d+) string: 12.3 10 0.018 5 11.006 7 .89 ============== pattern:(\d+\.?\d*) string: 12.3 10 0.018 5 11.006 7. 89 ============== pattern:(\d+|\d+\.\d+) string: 12.3 10 0.018 5 11.006 7 89 ============== pattern:-?(\d+|\d+\.\d+) string: 12.3 10 -0.018 -5 11.006 -7 89 ============== pattern:\([^()]*\) string: (12.3e+10-0.018e-5) (11.006-7.) ============== pattern:-?(\d+\.\d+)e[+-]\d+ string: 12.3e+10 -0.018e-5 ============== pattern:-?((\d+|\d+\.\d+)|(\d+\.\d+)e[+-]\d+) string: 12.3e+10 -0.018e-5 11.006 -7 89 ============== -------------------------------- Process exited after 0.5831 seconds with return value 0 请按任意键继续. . .
附录：
特殊字符：
characters description matches . not newline any character exceptline terminators(LF, CR, LS, PS). \t tab (HT) a horizontal tab character (same as\u0009). \n newline (LF) a newline (line feed) character (same as\u000A). \v vertical tab (VT) a vertical tab character (same as\u000B). \f form feed (FF) a form feed character (same as\u000C). \r carriage return (CR) a carriage return character (same as\u000D). \cletter control code a control code character whosecode unit valueis the same as the remainder of dividing thecode unit valueofletterby 32. For example:\cais the same as\u0001,\cbthe same as\u0002, and so on... \xhh ASCII character a character whosecode unit valuehas an hex value equivalent to the two hex digitshh. For example:\x4cis the same asL, or\x23the same as#. \uhhhh unicode character a character whosecode unit valuehas an hex value equivalent to the four hex digitshhhh. \0 null a null character (same as\u0000). \int backreference the result of the submatch whose opening parenthesis is theint-th (intshall begin by a digit other than0). Seegroupsbelow for more info. \d digit a decimal digit character \D not digit any character that is not a decimal digit character \s whitespace a whitespace character \S not whitespace any character that is not a whitespace character \w word an alphanumeric or underscore character \W not word any character that is not an alphanumeric or underscore character \character character the charactercharacteras it is, without interpreting its special meaning within a regex expression. Anycharactercan be escaped except those which form any of the special character sequences above. Needed for:^ $ \ . * + ? ( ) [ ] { } | [class] character class the target character is part of the class [^class] negated character class the target character is not part of the class
数量：
characters times effects * 0 or more The preceding atom is matched 0 or more times. + 1 or more The preceding atom is matched 1 or more times. ? 0 or 1 The preceding atom is optional (matched either 0 times or once). {int} int The preceding atom is matched exactlyinttimes. {int,} intor more The preceding atom is matchedintor more times. {min,max} betweenminandmax The preceding atom is matched at leastmintimes, but not more thanmax.
分组：
characters description effects (subpattern) Group Creates a backreference. (?:subpattern) Passive group Does not create a backreference.
其他：
characters description condition for match ^ Beginning of line Either it is the beginning of the target sequence, or follows aline terminator. $ End of line Either it is the end of the target sequence, or precedes aline terminator. | Separator Separates two alternative patterns or subpatterns..
