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| Classes | ||||
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basic_regex::mark_count | ||||
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| Deduction guides(C++17) |
unsigned mark_count()const; | (since C++11) | |
Returns the number of marked sub-expressions (also known as capture groups) within the regular expression.
Contents |
(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-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 subexpressionsr2 has 1 subexpressionsr3 has 2 subexpressionsr4 has 2 subexpressionsr5 has 1 subexpressionsr6 has 0 subexpressions
