std::match_results<BidirIt,Alloc>::operator[]
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(until C++20)
const_reference operator[]( size_type n ) const;
(since C++11)
If n > 0 and n < size(), returns a reference to the std::sub_match representing the part of the target sequence that was matched by the nth captured marked subexpression).
If n == 0, returns a reference to the std::sub_match representing the part of the target sequence matched by the entire matched regular expression.
if n >= size(), returns a reference to a std::sub_match representing an unmatched sub-expression (an empty subrange of the target sequence).
ready() must be true. Otherwise, the behavior is undefined.
Contents
[edit] Parameters
n
-
integral number specifying which match to return
[edit] Return value
Reference to the std::sub_match representing the specified matched subrange within the target sequence.
[edit] Example
Run this code
#include <iostream> #include <regex> #include <string> int main() { std::string target("baaaby"); std::smatch sm; std::regex re1("a(a)*b"); std::regex_search (target, sm, re1); std::cout << "entire match: " << sm[0] << '\n' << "submatch #1: " << sm[1] << '\n'; std::regex re2("a(a*)b"); std::regex_search (target, sm, re2); std::cout << "entire match: " << sm[0] << '\n' << "submatch #1: " << sm[1] << '\n'; }
Output:
entire match: aaab submatch #1: a entire match: aaab submatch #1: aa