std::basic_string_view<CharT,Traits>::starts_with

 

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Strings library

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basic_string

basic_string_view (C++17)

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std::basic_string_view

Member functions basic_string_view::basic_string_view    basic_string_view::operator= Iterators basic_string_view::beginbasic_string_view::cbegin basic_string_view::endbasic_string_view::cend basic_string_view::rbeginbasic_string_view::crbegin basic_string_view::rendbasic_string_view::crend Capacity basic_string_view::sizebasic_string_view::length basic_string_view::max_size basic_string_view::empty Operations basic_string_view::copy basic_string_view::substr basic_string_view::compare basic_string_view::starts_with (C++20) basic_string_view::ends_with (C++20) basic_string_view::contains (C++23) basic_string_view::find basic_string_view::rfind basic_string_view::find_first_of basic_string_view::find_last_of basic_string_view::find_first_not_of basic_string_view::find_last_not_of

Element access basic_string_view::at basic_string_view::operator[] basic_string_view::front basic_string_view::back basic_string_view::data Modifiers basic_string_view::remove_prefix basic_string_view::remove_suffix basic_string_view::swap Constants basic_string_view::npos Non-member functions operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20) operator<< operator""sv Helper classes hash<std::string_view>hash<std::wstring_view>hash<std::u8string_view>hash<std::u16string_view>hash<std::u32string_view> (C++20) Deduction guides(C++20)

 

constexprbool starts_with( basic_string_view sv )constnoexcept;	(1)	(since C++20)
constexprbool starts_with( CharT ch )constnoexcept;	(2)	(since C++20)
constexprbool 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(){usingnamespace 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 (C++20)	checks if the string view ends with the given suffix (public member function)
starts_with (C++20)	checks if the string starts with the given prefix (public member function of std::basic_string<CharT,Traits,Allocator>)
ends_with (C++20)	checks if the string ends with the given suffix (public member function of std::basic_string<CharT,Traits,Allocator>)
contains (C++23)	checks if the string contains the given substring or character (public member function of std::basic_string<CharT,Traits,Allocator>)
contains (C++23)	checks if the string view contains the given substring or character (public member function)
compare	compares two views (public member function)