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Difference between revisions of "cpp/string/basic string view/contains"

From cppreference.com
m (auto main() -> int -> int main())
m (→‎Example: simplify.)
 
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===Example===
 
===Example===
−
{{example|
+
{{example
 
|code=
 
|code=
−
#include <iostream>
 
 
#include <string_view>
 
#include <string_view>
 +
  
−
int main()
+
−
{
+
(
−
     using namespace std::literals;
+
)
 +
 +
     :
  
−
     std::cout
+
    
−
        << std::boolalpha
+
 +
  
−
        // bool contains(basic_string_view x) const noexcept;
+
// bool contains(x) const;
−
        << "https://cppreference.com"sv.contains("cpp"sv) << ' ' // true
+
:".contains("") true
−
        << "https://cppreference.com"sv.contains("java"sv) << ' ' // false
+
:".contains("") false
 +
  
−
        // bool contains(CharT x) const noexcept;
+
() }
−
        << "C++23"sv.contains('+') << ' ' // true
+
−
        << "C++23"sv.contains('-') << ' ' // false
+
−
 
+
−
        // bool contains(const CharT* x) const;
+
−
        << std::string_view("basic_string_view").contains("string") << ' '  // true
+
−
        << std::string_view("basic_string_view").contains("String") << '\n'; // false
+
−
}
+
−
|output=
+
−
true false true false true false
+
 
}}
 
}}
  

Latest revision as of 15:31, 13 June 2023

 
C++
 
Strings library
 
std::basic_string_view
 
constexpr bool contains( basic_string_view sv ) const noexcept;
 (1) (since C++23)
constexpr bool contains( CharT c ) const noexcept;
 (2) (since C++23)
constexpr bool contains( const CharT* s ) const;
 (3) (since C++23)

Checks if the string view contains the given substring, where

1) the substring is a string view.
2) the substring is a single character.
3) the substring is a null-terminated character string.

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

Contents

[edit] Parameters

sv - a string view
c - a single character
s - a null-terminated character string

[edit] Return value

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

[edit] Notes

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

[edit] Example

Run this code
#include <string_view>
using namespace std::literals;
 
static_assert
(
    // bool contains(basic_string_view x) const noexcept;
    "https://cppreference.com"sv.contains("cpp"sv) == true and
    "https://cppreference.com"sv.contains("php"sv) == false and
 
    // bool contains(CharT x) const noexcept;
    "C++23"sv.contains('+') == true and
    "C++23"sv.contains('-') == false and
 
    // bool contains(const CharT* x) const;
    std::string_view("basic_string_view").contains("string") == true and
    std::string_view("basic_string_view").contains("String") == false
);
 
int main() {}

[edit] See also

(C++20)
 checks if the string view starts with the given prefix
(public member function) [edit]
(C++20)
 checks if the string view ends with the given suffix
(public member function) [edit]
find characters in the view
(public member function) [edit]
returns a substring
(public member function) [edit]
(C++23)
 checks if the string contains the given substring or character
(public member function of std::basic_string<CharT,Traits,Allocator>) [edit]
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