std::holds_alternative
Defined in header <variant> |
||
|---|---|---|
template< class T, class... Types > constexpr bool holds_alternative( const std::variant<Types...>& v ) noexcept; |
(since C++17) |
Checks if the variant v holds the alternative T. The call is ill-formed if T does not appear exactly once in Types...
Parameters
| v | - | variant to examine |
Return value
true if the variant currently holds the alternative T, false otherwise.
Example
#include <variant>
#include <string>
#include <iostream>
int main()
{
std::variant<int, std::string> v = "abc";
std::cout << std::boolalpha
<< "variant holds int? "
<< std::holds_alternative<int>(v) << '\n'
<< "variant holds string? "
<< std::holds_alternative<std::string>(v) << '\n';
}
Output:
variant holds int? false variant holds string? true
See also
| returns the zero-based index of the alternative held by the variant (public member function) |
|
|
(C++17)
|
reads the value of the variant given the index or the type (if the type is unique), throws on error (function template) |
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https://en.cppreference.com/w/cpp/utility/variant/holds_alternative
