std::match_results<BidirIt,Alloc>::operator[]

 

C++

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text_encoding (C++26)

 

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match_results (C++11)

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std::match_results

Member functions

match_results::match_results

match_results::~match_results

match_results::operator=

match_results::get_allocator

State

match_results::ready

Element access

match_results::size

match_results::max_size

match_results::empty

match_results::length

match_results::position

match_results::str

match_results::operator[]

match_results::prefix

match_results::suffix

Iterators

match_results::beginmatch_results::cbegin

match_results::endmatch_results::cend

Format

match_results::format

Modifiers

match_results::swap

Non-member functions

operator==operator!= (until C++20)

swap(std::match_results)

 

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 n^th 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.

Parameters

n

-

integral number specifying which match to return

Return value

Reference to the std::sub_match representing the specified matched subrange within the target sequence.

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

See also

str	returns the sequence of characters for the particular sub-match (public member function)

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