std::basic_string_view<CharT,Traits>::starts_with
From cppreference.com
< cpp | string | basic string view
C++
Feature test macros (C++20)
Concepts library (C++20)
Metaprogramming library (C++11)
Ranges library (C++20)
Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)
std::basic_string_view
basic_string_view::starts_with
(C++20)
(C++20)
(C++23)
Constants
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)
Deduction guides (C++20)
constexpr bool starts_with( basic_string_view 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 view begins with the given prefix, where
1) the prefix is a string view. Effectively returns basic_string_view(data(), std::min (size(), sv.size())) == sv.
2) the prefix is a single character. Effectively returns !empty() && Traits::eq(front(), ch).
3) the prefix is a null-terminated character string. Effectively returns starts_with(basic_string_view(s)).
Contents
[edit] Parameters
sv
-
a string view which may be a result of implicit conversion from
std::basic_string
ch
-
a single character
s
-
a null-terminated character string
[edit] Return value
true if the string view 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_view> int main() { using namespace std::literals; assert ("" // (1) starts_with( basic_string_view ) && "https://cppreference.com"sv.starts_with("http"sv) == true && "https://cppreference.com"sv.starts_with("ftp"sv) == false // (2) starts_with( CharT ) && "C++20"sv.starts_with('C') == true && "C++20"sv.starts_with('J') == false // (3) starts_with( const CharT* ) && std::string_view ("string_view").starts_with("string") == true && std::string_view ("string_view").starts_with("String") == false ); }
[edit] See also
(C++20)
(public member function of
std::basic_string<CharT,Traits,Allocator>) [edit]
(C++20)
(public member function of
std::basic_string<CharT,Traits,Allocator>) [edit]
(C++23)
(public member function of
std::basic_string<CharT,Traits,Allocator>) [edit]
(C++23)
(public member function) [edit]