:idprefix: unordered_map_

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_T_

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`BOOST_UNORDERED_ENABLE_SERIALIZATION_COMPATIBILITY_V0`

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```c++ unordered_map(); ```

Postconditions:;; `size() == 0` Requires:;; If the defaults are used, `hasher`, `key_equal` and `allocator_type` need to be https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^].

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Postconditions:;; `size() == 0` Requires:;; If the defaults are used, `hasher`, `key_equal` and `allocator_type` need to be https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^].

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Requires:;; `value_type` is copy constructible