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 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)).

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

Return value¶

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

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()

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
);
}

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
(public member function)