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regex_replace Function

Replaces matched regular expressions.

template<class OutIt, class BidIt, class RXtraits, class Alloc, class Elem>
    OutIt regex_replace(OutIt out,
        BidIt first, BidIt last,
        const basic_regex<Elem, RXtraits, Alloc>& re,
        const basic_string<Elem>& fmt,
        match_flag_type flags = match_default);
template<class RXtraits, class Alloc, class Elem>
    basic_string<Elem> regex_replace(const basic_string<Elem>& str,
        const basic_regex<Elem, RXtraits, Alloc>& re,
        const basic_string<Elem>& fmt,
        match_flag_type flags = match_default);

OutIt

The iterator type for replacements.

BidIt

The iterator type for submatches.

RXtraits

Traits class for elements.

Alloc

The regular expression allocator class.

Elem

The type of elements to match.

flags

Flags for matches.

first

Beginning of sequence to match.

fmt

The format for replacements.

last

End of sequence to match.

out

The output iterator.

re

The regular expression to match.

str

String to match.

The first function constructs a regex_iterator Class object iter(first, last, re, flags) and uses it to split its input range [first, last) into a series of subsequences T0M0T1M1...TN-1MN-1TN, where Mn is the nth match detected by the iterator. If no matches are found, T0 is the entire input range and N is zero. If (flags & format_first_only) != 0 only the first match is used, T1 is all of the input text that follows the match, and N is 1. For each i in the range [0, N), if (flags & format_no_copy) == 0 it copies the text in the range Ti to the iterator out. It then calls m.format(out, fmt, flags), where m is the match_results object returned by the iterator object iter for the subsequence Mi. Finally, if (flags & format_no_copy) == 0 it copies the text in the range TN to the iterator out. The function returns out.

The second function constructs a local variable result of type basic_string<charT> and calls regex_replace(back_inserter(result), str.begin(), str.end(), re, fmt, flags). It returns result.

 

// std_tr1__regex__regex_replace.cpp 
// compile with: /EHsc 
#include <regex> 
#include <iostream> 
 
int main() 
    { 
    char buf[20]; 
    const char *first = "axayaz"; 
    const char *last = first + strlen(first); 
    std::regex rx("a"); 
    std::string fmt("A"); 
    std::regex_constants::match_flag_type fonly = 
        std::regex_constants::format_first_only; 
 
    *std::regex_replace(&buf[0], first, last, rx, fmt) = '\0'; 
    std::cout << "replacement == " << &buf[0] << std::endl; 
 
    *std::regex_replace(&buf[0], first, last, rx, fmt, fonly) = '\0'; 
    std::cout << "replacement == " << &buf[0] << std::endl; 
 
    std::string str("adaeaf"); 
    std::cout << "replacement == " 
        << std::regex_replace(str, rx, fmt) << std::endl; 
 
    std::cout << "replacement == " 
        << std::regex_replace(str, rx, fmt, fonly) << std::endl; 
 
    return (0); 
    } 
 
replacement == AxAyAz
replacement == Axayaz
replacement == AdAeAf
replacement == Adaeaf

Header: <regex>

Namespace: std

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