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

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 Comment
__cpp_lib_string_contains 202011L (C++23) contains functions

Example

#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

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

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