std::basic_string<CharT,Traits,Allocator>::contains

 

C++

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Named requirements

Feature test macros (C++20)

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Concepts library (C++20)

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Technical specifications

Symbols index

External libraries

 

Strings library

Null-terminated strings

Byte strings

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Wide strings

Classes

basic_string

basic_string_view (C++17)

char_traits

 

std::basic_string

Member functions basic_string::basic_string basic_string::~basic_string basic_string::operator= basic_string::assign basic_string::assign_range (C++23) basic_string::get_allocator Element access basic_string::at basic_string::operator[] basic_string::front (DR*) basic_string::back (DR*) basic_string::data basic_string::c_str basic_string::operator  basic_string_view (C++17) Iterators basic_string::beginbasic_string::cbegin (C++11) basic_string::endbasic_string::cend (C++11) basic_string::rbeginbasic_string::crbegin (C++11) basic_string::rendbasic_string::crend (C++11) Capacity basic_string::empty basic_string::sizebasic_string::length basic_string::max_size basic_string::reserve basic_string::capacity basic_string::shrink_to_fit (DR*) Modifiers basic_string::clear basic_string::insert basic_string::insert_range (C++23) basic_string::erase basic_string::push_back basic_string::pop_back (DR*) basic_string::append basic_string::append_range (C++23) basic_string::operator+= basic_string::replace basic_string::replace_with_range (C++23) basic_string::copy basic_string::resize basic_string::resize_and_overwrite (C++23)   basic_string::swap

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constexpr bool     contains( std::basic_string_view<CharT,Traits> sv ) const noexcept;	(1)	(since C++23)
constexpr bool     contains( CharT ch ) const noexcept;	(2)	(since C++23)
constexpr bool     contains( const CharT* s ) const;	(3)	(since C++23)

Checks if the string contains the given substring. The substring may be one of the following:

1) A string view sv (which may be a result of implicit conversion from another std::basic_string).

2) A single character ch.

3) A null-terminated character string s.

All three overloads are equivalent to return find(x) != npos;, where x is the parameter.

Parameters

sv	-	a string view which may be a result of implicit conversion from another std::basic_string
ch	-	a single character
s	-	a null-terminated character string

Return value

true if the string contains the provided substring, false otherwise.

Notes

Feature-test macro	Value	Std	Feature
__cpp_lib_string_contains	202011L	(C++23)	contains functions

Example

Run this code

#include <iomanip>
#include <iostream>
#include <string>
#include <string_view>
#include <type_traits>
 
template<typename SubstrType>
void test_substring(const std::string& str, SubstrType subs)
{
    constexpr char delim = std::is_scalar_v<SubstrType> ? '\'' : '\"';
    std::cout << std::quoted(str)
              << (str.contains(subs) ? " contains "
                                     : " does not contain ")
              << std::quoted(std::string{subs}, delim) << '\n';
}
 
int main()
{
    using namespace std::literals;
 
    auto helloWorld = "hello world"s;
 
    test_substring(helloWorld, "hello"sv);
    test_substring(helloWorld, "goodbye"sv);
    test_substring(helloWorld, 'w');
    test_substring(helloWorld, 'x');
}

Output:

"hello world" contains "hello"
"hello world" does not contain "goodbye"
"hello world" contains 'w'
"hello world" does not contain 'x'

See also

starts_with (C++20)	checks if the string starts with the given prefix (public member function)
ends_with (C++20)	checks if the string ends with the given suffix (public member function)
find	finds the first occurrence of the given substring (public member function)
substr	returns a substring (public member function)
contains (C++23)	checks if the string view contains the given substring or character (public member function of std::basic_string_view<CharT,Traits>)