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std::basic_string_view::starts_with(3) | C++ Standard Libary | std::basic_string_view::starts_with(3) |
NAME¶
std::basic_string_view::starts_with - std::basic_string_view::starts_with
Synopsis¶
constexpr bool starts_with( basic_string_view sv ) const
noexcept; (1) (since C++20)
constexpr bool starts_with( CharT c ) 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 substr(0, sv.size()) ==
sv
2) the prefix is a single character. Effectively returns !empty() &&
Traits::eq(front(), c)
3) the prefix is a null-terminated character string. Effectively returns
starts_with(basic_string_view(s))
Parameters¶
sv - a string view which may be a result of implicit conversion
from
std::basic_string
c - a single character
s - a null-terminated character string
Return value¶
true if the string view begins with the provided prefix, false otherwise.
Notes¶
Feature-test macro: __cpp_lib_starts_ends_with
Example¶
// Run this code
#include <iostream>
#include <string_view>
auto main() -> int
{
using namespace std::literals;
std::cout
<< std::boolalpha
// bool starts_with(basic_string_view x) const noexcept;
<<
"https://cppreference.com"sv.starts_with("http"sv)
<< ' ' // true
<<
"https://cppreference.com"sv.starts_with("ftp"sv)
<< ' ' // false
// bool starts_with(CharT x) const noexcept;
<< "C++20"sv.starts_with('C') << ' ' // true
<< "C++20"sv.starts_with('J') << ' ' // false
// bool starts_with(const CharT* x) const;
<<
std::string_view("string_view").starts_with("string")
<< ' ' // true
<<
std::string_view("string_view").starts_with("String")
<< ' ' // false
<< '\n';
}
Output:¶
true false true false true false
See also¶
ends_with checks if the string view ends with the given suffix
(C++20) (public member function)
starts_with checks if the string starts with the given prefix
(C++20) (public member function of
std::basic_string<CharT,Traits,Allocator>)
ends_with checks if the string ends with the given suffix
(C++20) (public member function of
std::basic_string<CharT,Traits,Allocator>)
contains checks if the string contains the given substring or character
(C++23) (public member function of
std::basic_string<CharT,Traits,Allocator>)
contains checks if the string view contains the given substring or character
(C++23) (public member function)
compare compares two views
(C++17) (public member function)
2022.07.31 | http://cppreference.com |