C++ Regex Library - regex_replace

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Description

It makes a copy of the target sequence (the subject) with all matches of the regular expression rgx (the pattern) replaced by fmt (the replacement). The target sequence is either s or the character sequence between first and last, depending on the version used.

Declaration

Following is the declaration for std::regex_replace.

template <class traits, class charT>
   basic_string<charT>regex_replace (const charT* s,
          const basic_regex<charT,traits>& rgx,
          const charT* fmt,

C++11

template <class traits, class charT>
   basic_string<charT>regex_replace (const charT* s,
          const basic_regex<charT,traits>& rgx,
          const charT* fmt,

C++14

template <class traits, class charT>
   basic_string<charT>regex_replace (const charT* s,
          const basic_regex<charT,traits>& rgx,
          const charT* fmt,

Parameters

• s − It is a string with the target sequence.

• rgx − It is a basic_regex object to match.

• flags − It is used to control how rgx is matched.

• m − It is an object of a match_results type.

Return Value

It returns a string object with the resulting sequence.

Exceptions

No-noexcept − this member function never throws exceptions.

Example

In below example for std::regex_replace.

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

int main () {
   std::string s ("there is a subsequence in the string\n");
   std::regex e ("\\b(sub)([^ ]*)");

   std::cout << std::regex_replace (s,e,"sub-$2");
  
   std::string result;
   std::regex_replace (std::back_inserter(result), s.begin(), s.end(), e, "$2");
   std::cout << result;

   std::cout << std::regex_replace (s,e,"$1 and $2",std::regex_constants::format_no_copy);
   std::cout << std::endl;

   return 0;
}

The output should be like this −

there is a sub-sequence in the string
there is a sequence in the string
sub and sequence