unsigned mark_count() const; | (since C++11) |
Returns the number of marked sub-expressions (also known as capture groups) within the regular expression.
(none).
The number of marked sub-expressions within the regular expression.
May throw implementation-defined exceptions.
#include <iostream>
#include <regex>
int main()
{
std::regex r1{"abcde"};
std::cout << "r1 has " << r1.mark_count() << " subexpressions" << '\n';
// Expected: 0
std::regex r2{"ab(c)de"};
std::cout << "r2 has " << r2.mark_count() << " subexpressions" << '\n';
// Expected: 1
std::regex r3{"a(bc)d(e)"};
std::cout << "r3 has " << r3.mark_count() << " subexpressions" << '\n';
// Expected: 2
// nested sub-expressions
std::regex r4{"abc(de(fg))"};
std::cout << "r4 has " << r4.mark_count() << " subexpressions" << '\n';
// Expected: 2
// escaped parentheses
std::regex r5{"a(bc\\(\\)de)"};
std::cout << "r5 has " << r5.mark_count() << " subexpressions" << '\n';
// Expected: 1
// using nosubs flag
std::regex r6 {"ab(c)de", std::regex_constants::nosubs};
std::cout << "r6 has " << r6.mark_count() << " subexpressions" << '\n';
// Expected: 0
}Output:
r1 has 0 subexpressions r2 has 1 subexpressions r3 has 2 subexpressions r4 has 2 subexpressions r5 has 1 subexpressions r6 has 0 subexpressions
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