std::basic_string<CharT,Traits,Allocator>::starts_with

 

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basic_string_view (C++17)

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std::basic_string

Member functions basic_string::basic_string basic_string::~basic_string basic_string::operator= basic_string::assign basic_string::assign_range (C++23) basic_string::get_allocator Element access basic_string::at basic_string::operator[] basic_string::front (DR*) basic_string::back (DR*) basic_string::data basic_string::c_str basic_string::operator  basic_string_view (C++17) Iterators basic_string::beginbasic_string::cbegin (C++11) basic_string::endbasic_string::cend (C++11) basic_string::rbeginbasic_string::crbegin (C++11) basic_string::rendbasic_string::crend (C++11) Capacity basic_string::empty basic_string::sizebasic_string::length basic_string::max_size basic_string::reserve basic_string::capacity basic_string::shrink_to_fit (DR*) Modifiers basic_string::clear basic_string::insert basic_string::insert_range (C++23) basic_string::erase basic_string::push_back basic_string::pop_back (DR*) basic_string::append basic_string::append_range (C++23) basic_string::operator+= basic_string::replace basic_string::replace_with_range (C++23) basic_string::copy basic_string::resize basic_string::resize_and_overwrite (C++23)   basic_string::swap

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constexpr bool     starts_with( std::basic_string_view<CharT,Traits> 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 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.

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

Return value

true if the string 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>
#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)
    );
}

See also

ends_with (C++20)	checks if the string ends with the given suffix (public member function)
starts_with (C++20)	checks if the string view starts with the given prefix (public member function of std::basic_string_view<CharT,Traits>)
ends_with (C++20)	checks if the string view ends with the given suffix (public member function of std::basic_string_view<CharT,Traits>)
contains (C++23)	checks if the string contains the given substring or character (public member function)
contains (C++23)	checks if the string view contains the given substring or character (public member function of std::basic_string_view<CharT,Traits>)
compare	compares two strings (public member function)
substr	returns a substring (public member function)