std::holds_alternative
From cppreference.com
C++
Utilities library
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std::variant
Member functions | ||||
Observers | ||||
Modifiers | ||||
Visitation | ||||
(C++26)
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Non-member functions | ||||
holds_alternative | ||||
Helper classes | ||||
Helper objects | ||||
Defined in header <variant>
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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
Example
Run this code
#include <cassert> #include <string> #include <variant> int main() { std::variant<int, std::string> v = "abc"; assert(not std::holds_alternative<int>(v)); assert(std::holds_alternative<std::string>(v)); }
See also
returns the zero-based index of the alternative held by the variant (public member function) |
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(C++17)
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reads the value of the variant given the index or the type (if the type is unique), throws on error (function template) |