match_results::size
Counts number of submatches.
size_type size() const;
Remarks
The member function returns one more than the number of capture groups in the regular expression that was used for the search, or zero if no search has been made.
Example
// std_tr1__regex__match_results_size.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