match_results::format
Formats submatches.
Syntax
template<class OutIt>
OutIt format(OutIt out,
const string_type& fmt, match_flag_type flags = format_default) const;
string_type format(const string_type& fmt, match_flag_type flags = format_default) const;
Parameters
OutIt
The output iterator type.out
The output stream to write to.fmt
The format string.flags
The format flags.
Remarks
Each member function generates formatted text under the control of the format fmt. The first member function writes the formatted text to the sequence defined by its argument out and returns out. The second member function returns a string object holding a copy of the formatted text.
To generate formatted text. literal text in the format string is ordinarily copied to the target sequence. Each escape sequence in the format string is replaced by the text that it represents. The details of the copying and replacement are controlled by the format flags passed to the function.
Example
// std__regex__match_results_format.cpp
// compile with: /EHsc
#include <regex>
#include <iostream>
int main()
{
std::regex rx("c(a*)|(b)");
std::cmatch mr;
std::regex_search("xcaaay", mr, rx);
std::cout << "prefix: matched == " << std::boolalpha
<< mr.prefix().matched
<< ", value == " << mr.prefix() << std::endl;
std::cout << "whole match: " << mr.length() << " chars, value == "
<< mr.str() << std::endl;
std::cout << "suffix: matched == " << std::boolalpha
<< mr.suffix().matched
<< ", value == " << mr.suffix() << std::endl;
std::cout << std::endl;
std::string fmt("\"c(a*)|(b)\" matched \"$0\"\n"
"\"(a*)\" matched \"$1\"\n"
"\"(b)\" matched \"$2\"\n");
std::cout << mr.format(fmt) << std::endl;
std::cout << std::endl;
// index through submatches
for (size_t n = 0; n < mr.size(); ++n)
{
std::cout << "submatch[" << n << "]: matched == " << std::boolalpha
<< mr[n].matched <<
" at position " << mr.position(n) << std::endl;
std::cout << " " << mr.length(n)
<< " chars, value == " << mr[n] << std::endl;
}
std::cout << std::endl;
// iterate through submatches
for (std::cmatch::iterator it = mr.begin(); it != mr.end(); ++it)
{
std::cout << "next submatch: matched == " << std::boolalpha
<< it->matched << std::endl;
std::cout << " " << it->length()
<< " chars, value == " << *it << std::endl;
}
std::cout << std::endl;
// other members
std::cmatch mr1(mr);
mr = mr1;
mr.swap(mr1);
char buf[10];
*mr.format(&buf[0], "<$0>") = '\0';
std::cout << &buf[0] << std::endl;
std::cout << "empty == " << std::boolalpha << mr.empty() << std::endl;
std::cmatch::allocator_type al = mr.get_allocator();
std::cmatch::string_type str = std::string("x");
std::cmatch::size_type maxsiz = mr.max_size();
std::cmatch::char_type ch = 'x';
std::cmatch::difference_type dif = mr.begin() - mr.end();
std::cmatch::const_iterator cit = mr.begin();
std::cmatch::value_type val = *cit;
std::cmatch::const_reference cref = val;
std::cmatch::reference ref = val;
maxsiz = maxsiz; // to quiet "unused" warnings
if (ref == cref)
ch = ch;
dif = dif;
return (0);
}
prefix: matched == true, value == x whole match: 4 chars, value == caaa suffix: matched == true, value == y "c(a*)|(b)" matched "caaa" "(a*)" matched "aaa" "(b)" matched "" submatch[0]: matched == true at position 1 4 chars, value == caaa submatch[1]: matched == true at position 2 3 chars, value == aaa submatch[2]: matched == false at position 6 0 chars, value == next submatch: matched == true 4 chars, value == caaa next submatch: matched == true 3 chars, value == aaa next submatch: matched == false 0 chars, value == <caaa> empty == false
Requirements
Header: <regex>
Namespace: std