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

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constexpr bool
    starts_with( std::basic_string_view<CharT,Traits> sv ) const noexcept;
(1) (since C++20)
constexpr bool
    starts_with( CharT ch ) const noexcept;
(2) (since C++20)
constexpr bool
    starts_with( const CharT* s ) const;
(3) (since C++20)

Checks if the string begins with the given prefix. The prefix 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 effectively return std::basic_string_view<CharT, Traits>(data(), size()).starts_with(x), where x is the parameter.

Contents

[edit] 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

[edit] Return value

true if the string begins with the provided prefix, false otherwise.

[edit] Notes

Feature-test macro Value Std Feature
__cpp_lib_starts_ends_with 201711L (C++20) String prefix and suffix checking: starts_with() and ends_with()

[edit] Example

#include <cassert>
#include <string>
#include <string_view>
 
int main()
{
    using namespace std::literals;
 
    const auto str = "Hello, C++20!"s;
 
    assert
    (""
        && str.starts_with("He"sv)  // (1)
        && !str.starts_with("he"sv) // (1)
        && str.starts_with("He"s)   // (1) implicit conversion string to string_view
        && !str.starts_with("he"s)  // (1) implicit conversion string to string_view
        && str.starts_with('H')     // (2)
        && !str.starts_with('h')    // (2)
        && str.starts_with("He")    // (3)
        && !str.starts_with("he")   // (3)
    );
}

[edit] See also

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