# std::hash <std::variant>

From cppreference.com
< cpp‎ | utility‎ | variant

Defined in header `<variant>` |  |
template <class... Types> struct hash<std::variant<Types...>>; |  | (since C++17)

The template specialization of std::hash for the std::variant template allows users to obtain hashes of `variant` objects.

The specialization std::hash<std::variant<Types...>> is enabled (see std::hash) if every specialization in std::hash<std::remove_const_t<Types>>... is enabled, and is disabled otherwise.

The member functions of this specialization are not guaranteed to be noexcept.

### Template parameters

Types | - | the types of the alternatives supported by the `variant` object

### Notes

Unlike `std::hash<std::optional>`, hash of a variant does not typically equal the hash of the contained value; this makes it possible to distinguish std::variant<int, int> holding the same value as different alternatives.

### Example

| This section is incomplete Reason: no example

### See also

hash (C++11) | hash function object (class template)

Retrieved from "http://en.cppreference.com/mwiki/index.php?title=cpp/utility/variant/hash&oldid=91128"
Category:

- Todo no example