std::regex_replace

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regex_replace
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Defined in header <regex>
template < class OutputIt, class BidirIt, class Traits, class CharT,

class STraits, class SAlloc >
OutputIt regex_replace( OutputIt out, BidirIt first, BidirIt last,
const std::basic_regex <CharT, Traits> & re,
const std::basic_string <CharT, STraits, SAlloc> & fmt,
std::regex_constants::match_flag_type flags =

std::regex_constants::match_default ) ;
(1) (since C++11)
template < class OutputIt, class BidirIt, class Traits, class CharT >

OutputIt regex_replace( OutputIt out, BidirIt first, BidirIt last,
const std::basic_regex <CharT, Traits> & re,
const CharT* fmt,
std::regex_constants::match_flag_type flags =

std::regex_constants::match_default ) ;
(2) (since C++11)
template < class Traits, class CharT,

class STraits, class SAlloc, class FTraits, class FAlloc >
std::basic_string <CharT, STraits, SAlloc>
    regex_replace( const std::basic_string <CharT, STraits, SAlloc> & str,
const std::basic_regex <CharT, Traits> & re,
const std::basic_string <CharT, FTraits, FAlloc> & fmt,
std::regex_constants::match_flag_type flags =

std::regex_constants::match_default ) ;
(3) (since C++11)
template < class Traits, class CharT, class STraits, class SAlloc >

std::basic_string <CharT, STraits, SAlloc>
    regex_replace( const std::basic_string <CharT, STraits, SAlloc> & str,
const std::basic_regex <CharT, Traits> & re,
const CharT* fmt,
std::regex_constants::match_flag_type flags =

std::regex_constants::match_default ) ;
(4) (since C++11)
template < class Traits, class CharT, class STraits, class SAlloc >

std::basic_string <CharT>
    regex_replace( const CharT* s, const std::basic_regex <CharT, Traits> & re,
const std::basic_string <CharT, STraits, SAlloc> & fmt,
std::regex_constants::match_flag_type flags =

std::regex_constants::match_default ) ;
(5) (since C++11)
template < class Traits, class CharT >

std::basic_string <CharT>
    regex_replace( const CharT* s, const std::basic_regex <CharT, Traits> & re,
const CharT* fmt,
std::regex_constants::match_flag_type flags =

std::regex_constants::match_default ) ;
(6) (since C++11)

regex_replace uses the regular expression re to perform substitution on the target character sequence:

1,2) Copies characters in the range [first, last) to out, replacing any sequences that match re with characters formatted by fmt. Equivalent to: 
using iter_type = std::regex_iterator<BidirIt, CharT, Traits>;
iter_type seq_begin(first, last, re, flags), seq_end;
 
using result_type = std::match_results<BidirIt>;
result_type m;
 
bool need_to_copy = (flags & std::regex_constants::format_no_copy) == 0;
bool format_all = (flags & std::regex_constants::format_first_only) != 0;
 
for (iter_type i = seq_begin; i != seq.end(); ++i)
{
    m = *i;
    if (need_to_copy)
        out = std::copy(m.prefix().first, m.prefix().second, out);
    if (format_all || i == seq_begin)
        out = /* replace-expr */
}
 
if (need_to_copy)
    out = m.ready()
              ? std::copy(m.suffix().first, m.suffix().second, out)
              : std::copy(first, last, out);
 
return out;
1) The expression /* replace-expr */ is m.format(out, fmt, flags)
2) The expression /* replace-expr */ is m.format (out, fmt, fmt + std::char_traits <CharT> :: length (fmt), flags)
3,4) Equivalent to std::basic_string <CharT, STraits, SAlloc> result;
regex_replace( std::back_inserter (result)
str.begin ( ), str.end ( ), re, fmt, flags) ;
return result;
5,6) Equivalent to std::basic_string <CharT, STraits, SAlloc> result;
regex_replace( std::back_inserter (result)
s, s + std::char_traits <CharT> :: length (s), re, fmt, flags) ;
return result;

Parameters

first, last - the target character range
str - the target std::string
s - the target null-terminated C-style string
re - the regular expression
fmt - the regex replacement format string, exact syntax depends on the value of flags
flags - flags used to determine how the match will be performed
out - output iterator to store the result of the replacement

Return value

As described above.

Exceptions

May throw std::regex_error to indicate an error condition.

Example

Run this code
#include <iostream>
#include <iterator>
#include <regex>
#include <string>
 
int main()
{
    std::string text = "Quick brown fox";
    std::regex vowel_re("a|e|i|o|u");
 
    // write the results to an output iterator
    std::regex_replace(std::ostreambuf_iterator<char>(std::cout),
                       text.begin(), text.end(), vowel_re, "*");
 
    // construct a string holding the results
    std::cout << '\n' << std::regex_replace(text, vowel_re, "[$&]") << '\n';
}

Output: 

Q**ck br*wn f*x
Q[u][i]ck br[o]wn f[o]x

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2213 C++11 out was not updated by the replacements out is updated

See also

(C++11)
 attempts to match a regular expression to any part of a character sequence
(function template)
(C++11)
 options specific to matching
(typedef)
replaces specified portion of a string
(public member function of std::basic_string<CharT,Traits,Allocator>)
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