std::match_results::prefix

C++

Language

Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

Regular expressions library

Classes

basic_regex (C++11)

sub_match (C++11)

match_results (C++11)

Algorithms

regex_match (C++11)

regex_search (C++11)

regex_replace (C++11)

Iterators

regex_iterator (C++11)

regex_token_iterator (C++11)

Exceptions

regex_error (C++11)

Traits

regex_traits (C++11)

Constants

syntax_option_type (C++11)

match_flag_type (C++11)

error_type (C++11)

Regex Grammar

Modified ECMAScript-262 (C++11)

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

const_reference prefix() const;		(since C++11)

Obtains a reference to the std::sub_match object representing the target sequence between the start of the beginning of the target sequence and the start of the entire match of the regular expression.

The behavior is undefined unless ready() == true

Parameters

(none)

Return value

Reference to the unmatched prefix.

Example

Run this code

#include <iostream>
#include <regex>
#include <string>

int main()
{
  std::regex re("a(a)*b");
  std::string target("baaaby");
  std::smatch sm;

  std::regex_search(target, sm, re);
  std::cout << sm.prefix().str() << '\n';
}

Output:

b