std::basic_regex<CharT,Traits>::mark_count
From cppreference.com
< cpp | regex | basic regex
unsigned mark_count()const; | (since C++11) | |
Returns the number of marked sub-expressions (also known as capture groups) within the regular expression.
Contents |
[edit]Parameters
(none)
[edit]Return value
The number of marked sub-expressions within the regular expression.
[edit]Exceptions
May throw implementation-defined exceptions.
[edit]Example
Run this code
#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-expressionsstd::regex r4{"abc(de(fg))"};std::cout<<"r4 has "<< r4.mark_count()<<" subexpressions"<<'\n';// Expected: 2 // Escaped parenthesesstd::regex r5{"a(bc\\(\\)de)"};std::cout<<"r5 has "<< r5.mark_count()<<" subexpressions"<<'\n';// Expected: 1 // Using nosubs flagstd::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
