Difference between revisions of "cpp/regex"
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< cpp
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if (std::regex_search(s, self_regex)) { | if (std::regex_search(s, self_regex)) { | ||
std::cout << "Text contains the phrase 'regular expressions'\n"; | std::cout << "Text contains the phrase 'regular expressions'\n"; | ||
| − | } | + | } |
std::regex word_regex("(\\S+)"); | std::regex word_regex("(\\S+)"); | ||
| Line 89: | Line 89: | ||
auto words_end = std::sregex_iterator(); | auto words_end = std::sregex_iterator(); | ||
| − | std::cout << "Found " | + | std::cout << "Found " |
| − | << std::distance(words_begin, words_end) | + | << std::distance(words_begin, words_end) |
<< " words\n"; | << " words\n"; | ||
| Line 96: | Line 96: | ||
std::cout << "Words greater than " << N << " characters:\n"; | std::cout << "Words greater than " << N << " characters:\n"; | ||
for (std::sregex_iterator i = words_begin; i != words_end; ++i) { | for (std::sregex_iterator i = words_begin; i != words_end; ++i) { | ||
| − | std::smatch match = *i; | + | std::smatch match = *i; |
std::string match_str = match.str(); | std::string match_str = match.str(); | ||
if (match_str.size() > N) { | if (match_str.size() > N) { | ||
std::cout << " " << match_str << '\n'; | std::cout << " " << match_str << '\n'; | ||
| − | } | + | } |
| − | } | + | } |
| − | std::regex long_word_regex("(\\w{7,})"); | + | std::regex long_word_regex("(\\w{7,})"); |
std::string new_s = std::regex_replace(s, long_word_regex, "[$&]"); | std::string new_s = std::regex_replace(s, long_word_regex, "[$&]"); | ||
std::cout << new_s << '\n'; | std::cout << new_s << '\n'; | ||
Revision as of 15:04, 10 July 2013
| Defined in header
<regex> |
The regular expressions library provides a class that represents regular expressions, which are a kind of mini-language used to perform pattern matching within strings.
Also provided in the regular expressions library are utility classes that provide support for various algorithms, iterators, exceptions, and type traits.
Contents |
Main classes
These classes encapsulate a regular expression and the results of matching a regular expression within a target sequence of characters.
| (C++11) |
regular expression object (class template) |
| (C++11) |
identifies the sequence of characters matched by a sub-expression (class template) |
| (C++11) |
identifies one regular expression match, including all sub-expression matches (class template) |
Algorithms
These functions are used to apply the regular expression encapsulated in a regex to a target sequence of characters.
| (C++11) |
attempts to match a regular expression to an entire character sequence (function template) |
| (C++11) |
attempts to match a regular expression to any part of a character sequence (function template) |
| (C++11) |
replaces occurrences of a regular expression with formatted replacement text (function template) |
Iterators
The regex iterators are used to traverse the entire set of regular expression matches found within a sequence.
| (C++11) |
iterates through all regex matches within a character sequence (class template) |
| (C++11) |
iterates through the specified sub-expressions within all regex matches in a given string or through unmatched substrings (class template) |
Exceptions
This class defines the type of objects thrown as exceptions to report errors from the regular expressions library.
| (C++11) |
reports errors generated by the regular expressions library (class) |
Traits
The regex traits class is used to encapsulate the localizable aspects of a regex.
| (C++11) |
provides metainformation about a character type, required by the regex library (class template) |
Constants
| Defined in namespace
std::regex_constants | |
| (C++11) |
general options controlling regex behavior (typedef) |
| (C++11) |
options specific to matching (typedef) |
| (C++11) |
describes different types of matching errors (typedef) |
Example
Run this code
#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 greater 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 greater 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].
