std::basic_string<CharT,Traits,Allocator>::starts_with
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basic_string::starts_with
(C++20)
(C++20)
(C++23)
(C++20)(C++20)
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(C++11)
constexpr bool
starts_with( std::basic_string_view <CharT,Traits> sv ) const noexcept;
(1)
(since C++20)
starts_with( std::basic_string_view <CharT,Traits> sv ) const noexcept;
constexpr bool
starts_with( CharT ch ) const noexcept;
(2)
(since C++20)
starts_with( CharT ch ) const noexcept;
constexpr bool
starts_with( const CharT* s ) const;
(3)
(since C++20)
starts_with( const CharT* s ) const;
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
Run this code
#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)
(public member function of
std::basic_string_view<CharT,Traits>) [edit]
(C++20)
(public member function of
std::basic_string_view<CharT,Traits>) [edit]
(C++23)
(public member function) [edit]
(C++23)
(public member function of
std::basic_string_view<CharT,Traits>) [edit]