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

 

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basic_string

basic_string_view (C++17)

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std::basic_string

Member functions basic_string::basic_string basic_string::operator= basic_string::assign basic_string::get_allocator Element access basic_string::at basic_string::operator[] basic_string::front (C++11) basic_string::back (C++11) 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 (C++11)

Operations basic_string::clear basic_string::insert basic_string::erase basic_string::push_back basic_string::pop_back (C++11) basic_string::append basic_string::operator+= basic_string::compare basic_string::starts_with (C++20) basic_string::ends_with (C++20) basic_string::replace basic_string::substr basic_string::copy basic_string::resize basic_string::swap Search basic_string::find basic_string::rfind basic_string::find_first_of basic_string::find_first_not_of basic_string::find_last_of basic_string::find_last_not_of Constants basic_string::npos

Non-member functions operator+ swap(std::basic_string) operator""s (C++14) erase(std::basic_string)erase_if(std::basic_string) (C++20)(C++20) I/O operator<<operator>> getline Comparison operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20) Numeric conversion (C++11) stoistolstoll stoulstoull stofstodstold to_string to_wstring Helper classes hash<std::string>hash<std::wstring>hash<std::u32string>hash<std::u16string>hash<std::u8string> (C++11)(C++11)(C++11)(C++11)(C++20) hash<std::pmr::string>hash<std::pmr::wstring>hash<std::pmr::u32string>hash<std::pmr::u16string>hash<std::pmr::u8string> (C++20)(C++20)(C++20)(C++20)(C++20) Deduction guides(C++17)

 

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

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
c	-	a single character
s	-	a null-terminated character string

Return value

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

Example

Run this code

#include <iostream>
#include <string_view>
#include <string>
 
template <typename PrefixType>
void test_prefix_print(const std::string& str, PrefixType prefix)
{
    std::cout << '\'' << str << "' starts with '" << prefix << "': " <<
        str.starts_with(prefix) << '\n';
}
 
int main()
{
    std::boolalpha(std::cout);    
    auto helloWorld = std::string("hello world");
 
    test_prefix_print(helloWorld, std::string_view("hello"));
 
    test_prefix_print(helloWorld, std::string_view("goodby"));
 
    test_prefix_print(helloWorld, 'h');
 
    test_prefix_print(helloWorld, 'x');
}

Output:

'hello world' starts with 'hello': true
'hello world' starts with 'goodbye': false
'hello world' starts with 'h': true
'hello world' starts with 'x': false

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>)
compare	compares two strings (public member function)
substr	returns a substring (public member function)