std::basic_regex<CharT,Traits>::mark_count

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

Memory management library

Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution control library (C++26)

Technical specifications

Symbols index

External libraries

 

Text processing library

Localization library

Regular expressions library (C++11)

Formatting library (C++20)

Null-terminated sequence utilities

Byte strings

Multibyte strings

Wide strings

Primitive numeric conversions

to_chars (C++17) to_chars_result (C++17) from_chars (C++17) from_chars_result (C++17) chars_format (C++17)

Text encoding identifications

text_encoding (C++26)

 

Regular expressions library

Classes

basic_regex (C++11)

sub_match (C++11)

match_results (C++11)

Algorithms

regex_match (C++11)

regex_search (C++11)

regex_replace (C++11)

Iterators

regex_iterator (C++11)

regex_token_iterator (C++11)

Exceptions

regex_error (C++11)

Traits

regex_traits (C++11)

Constants

syntax_option_type (C++11)

match_flag_type (C++11)

error_type (C++11)

Regex Grammar

Modified ECMAScript-262 (C++11)

 

std::basic_regex

Member Functions

basic_regex::basic_regex

basic_regex::~basic_regex

basic_regex::operator=

basic_regex::assign

Observers

basic_regex::mark_count

basic_regex::flags

Locale

basic_regex::getloc

basic_regex::imbue

Modifiers

basic_regex::swap

Constants

Non-member Functions

swap(std::basic_regex)

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.

Parameters

(none)

Return value

The number of marked sub-expressions within the regular expression.

Exceptions

May throw implementation-defined exceptions.

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-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

Follow Lee on X/Twitter - Father, Husband, Serial builder creating AI, crypto, games & web tools. We are friends :) AI Will Come To Life!

Check out: eBank.nz (Art Generator) | Netwrck.com (AI Tools) | Text-Generator.io (AI API) | BitBank.nz (Crypto AI) | ReadingTime (Kids Reading) | RewordGame | BigMultiplayerChess | WebFiddle | How.nz | Helix AI Assistant