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# std::hash <std::experimental::optional>

From cppreference.com
< cpp‎ | experimental‎ | optional

| After reviewing national body comments to n3690, this library component was voted out from C++14 working paper into a separate Technical Specification. It is not a part of the draft C++14 as of n3797.

Defined in header `<experimental/optional>` |  |
template<class T> struct hash<std::experimental::optional<T>>; |  | (library fundamentals TS)

The template specialization of std::hash for the std::experimental::optional class allows users to obtain hashes of the values contained in `optional` objects.

### [edit] Template parameters

T | - | the type of the value contained in `optional` object. The specialization std::hash<T> must meet the requirements of class template `hash`.

### [edit] Example

| This section is incomplete Reason: no example

### [edit] See also

hash (C++11) | hash function object (class template) [edit]

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- Todo no example