std::get (std::variant)
Defined in header <variant>
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(1) | (since C++17) | |
template <std::size_t I, class... Types> constexpr std::variant_alternative_t< |
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template <std::size_t I, class... Types> constexpr std::variant_alternative_t< |
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template <std::size_t I, class... Types> constexpr std::variant_alternative_t< |
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template <std::size_t I, class... Types> constexpr std::variant_alternative_t< |
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(2) | (since C++17) | |
template <class T, class... Types> constexpr T& get(std::variant<Types...>& v); |
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template <class T, class... Types> constexpr T&& get(std::variant<Types...>&& v); |
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template <class T, class... Types> constexpr const T& get(const std::variant<Types...>& v); |
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template <class T, class... Types> constexpr const T&& get(const std::variant<Types...>&& v); |
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1) Index-based value accessor: If v.index() == I, returns a reference to the value stored in
v
. Otherwise, throws std::bad_variant_access. The call is ill-formed if I
is not a valid index in the variant.2) Type-based value accessor: If v holds the alternative
T
, returns a reference to the value stored in v
. Otherwise, throws std::bad_variant_access. The call is ill-formed if T
is not a unique element of Types...
.Parameters
I | - | index to look up |
Type | - | unique type to look up |
v | - | a variant |
Return value
Reference to the value stored in the variant.
Exceptions
1,2) Throws std::bad_variant_access on errors.
Example
Run this code
#include <variant> #include <string> int main() { std::variant<int, float> v{12}, w; int i = std::get<int>(v); w = std::get<int>(v); w = std::get<0>(v); // same effect as the previous line // std::get<double>(v); // error: no double in [int, float] // std::get<3>(v); // error: valid index values are 0 and 1 try { std::get<float>(w); // w contains int, not float: will throw } catch (std::bad_variant_access&) {} }
See also
(C++17) |
obtains a pointer to the value of a pointed-to variant given the index or the type (if unique), returns null on error (function template) |
tuple accesses specified element (function template) | |
accesses an element of an array (function template) | |
(C++11) |
accesses an element of a pair (function template) |