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std::hash

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< cpp‎ | memory‎ | unique ptr
Revision as of 15:41, 1 July 2013 by P12bot (Talk | contribs)

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template<class T, class Deleter> struct hash<unique_ptr<T, Deleter>>;
(since C++11)

The template specialization of std::hash for std::unique_ptr<T, Deleter> allows users to obtain hashes of objects of type std::unique_ptr<T, Deleter>.

For a given std::unique_ptr<T, Deleter> p, this specialization ensures that std::hash<std::unique_ptr<T, Deleter>>()(p) == std::hash<T*>()(p.get()).

[edit] Example

#include <iostream>
#include <memory>
#include <functional>
 
struct Foo {
    Foo() { std::cout << "Foo...\n"; }
    ~Foo() { std::cout << "~Foo...\n\n"; }
};
 
int main()
{
    Foo* foo = new Foo();
    std::unique_ptr<Foo> up(foo);
 
    std::cout << "hash(up):  " << std::hash<std::unique_ptr<Foo>>()(up) << '\n';
    std::cout << "hash(foo): " << std::hash<Foo*>()(foo) << '\n';
}

Output:

Foo...
hash(up):  3686401041
hash(foo): 3686401041
~Foo...

[edit] See also

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