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

From cppreference.com
< cpp‎ | string‎ | basic string
 
 
 
std::basic_string
 
bool starts_with(std::basic_string_view<CharT, Traits> x) const noexcept;
(1) (since C++20)
bool starts_with(CharT x) const noexcept;
(2) (since C++20)
bool starts_with(const CharT* x) const;
(3) (since C++20)

Checks if the string begins with the given prefix, where

1) the prefix is a string view (which may be a result of implicit conversion from another std::basic_string)
2) the prefix is a single character
3) the prefix is a C-style string

All three overloads effectively return std::basic_string_view<CharT, Traits>(data(), size()).starts_with(x);

Contents

[edit] Parameters

x - a character sequence or a single character to compare to the start of the string

[edit] Return value

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

[edit] Example

#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 'goodby': false
'hello world' starts with 'h': true
'hello world' starts with 'x': false

[edit] See also

(C++20)
checks if the string ends with the given suffix
(public member function) [edit]
checks if the string view starts with the given prefix
(public member function of std::basic_string_view<CharT,Traits>) [edit]
(C++20)
checks if the string view ends with the given suffix
(public member function of std::basic_string_view<CharT,Traits>) [edit]
compares two strings
(public member function) [edit]
returns a substring
(public member function) [edit]