C++11中也将正则表达式纳入了新标准的一部分，不仅如此，它还支持了6种不同的正则表达式的语法，分别是：`ECMASCRIPT`、`basic`、`extended`、`awk`、`grep和egrep`。其中`ECMASCRIPT`是默认的语法，具体使用哪种语法我们可以在构造正则表达式的时候指定。 正则表达式库提供表示正则表达式，这是一种用于字符串内执行模式匹配小型的语言的类。 主要的类：  **basic_regex**  regular expression object **sub_match**  identifies the sequence of characters matched by a sub-expression **match_results**  identifies one regular expression match, including all sub-expression matches 算法：  These functions are used to apply the regular expression encapsulated in a regex to a target sequence of characters. **regex_match**  attempts to match a regular expression to an entire character sequence **regex_search**  attempts to match a regular expression to any part of a character sequence **regex_replace**  replaces occurrences of a regular expression with formatted replacement text 迭代器：  The regex iterators are used to traverse the entire set of regular expression matches found within a sequence. **regex_iterator**  iterates through all regex matches within a character sequence **regex_token_iterator**  iterates through the specified sub-expressions within all regex matches in a given string or through unmatched substrings 异常：  This class defines the type of objects thrown as exceptions to report errors from the regular expressions library. **regex_error**  reports errors generated by the regular expressions library 例子代码： ~~~ #include <iostream> #include <iterator> #include <string> #include <regex> int main() { std::string s = "Some people, when confronted with a problem, think " "\"I know, I'll use regular expressions.\" " "Now they have two problems."; std::regex self_regex("REGULAR EXPRESSIONS", std::regex_constants::ECMAScript | std::regex_constants::icase); if (std::regex_search(s, self_regex)) { std::cout << "Text contains the phrase 'regular expressions'\n"; } std::regex word_regex("(\\S+)"); auto words_begin = std::sregex_iterator(s.begin(), s.end(), word_regex); auto words_end = std::sregex_iterator(); std::cout << "Found " << std::distance(words_begin, words_end) << " words\n"; const int N = 6; std::cout << "Words longer than " << N << " characters:\n"; for (std::sregex_iterator i = words_begin; i != words_end; ++i) { std::smatch match = *i; std::string match_str = match.str(); if (match_str.size() > N) { std::cout << " " << match_str << '\n'; } } std::regex long_word_regex("(\\w{7,})"); std::string new_s = std::regex_replace(s, long_word_regex, "[$&]"); std::cout << new_s << '\n'; } Output: Text contains the phrase 'regular expressions' Found 19 words Words longer than 6 characters: people, confronted problem, regular expressions." problems. Some people, when [confronted] with a [problem], think "I know, I'll use [regular] [expressions]." Now they have two [problems]. ~~~