std::basic_string<CharT,Traits,Allocator>::starts_with
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.
Notes
Feature testing macro: __cpp_lib_starts_ends_with.
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("goodbye"));
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
|
(C++20)
|
checks if the string ends with the given suffix (public member function) |
|
(C++20)
|
checks if the string view starts with the given prefix (public member function of std::basic_string_view<CharT,Traits>) |
|
(C++20)
|
checks if the string view ends with the given suffix (public member function of std::basic_string_view<CharT,Traits>) |
|
(C++23)
|
checks if the string contains the given substring or character (public member function) |
|
(C++23)
|
checks if the string view contains the given substring or character (public member function of std::basic_string_view<CharT,Traits>) |
| compares two strings (public member function) |
|
| returns a substring (public member function) |
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