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std::hash <std::unique_ptr>

std：：散列<std：：UNIQUE[医]PTR>

template struct hash>;​(since C++11)

模板的专门化std::hash为std::unique_ptr<T, Deleter>允许用户获取类型对象的散列。std::unique_ptr<T, Deleter>...

The specialization std::hash> is enabled (see std::hash) if std::hash::pointer> is enabled, and is disabled otherwise.(since C++17)

启用后，自C++17%29以来的%28用于给定std::unique_ptr<T, D> p，此专门化确保std::hash<std::unique_ptr<T, D>>()(p)==std::hash<typenamestd::unique_ptr<T, D>::pointer>()(p.get())...

这种专门化的成员函数不能保证为no，除非指针可能是一个花哨的指针，并且它的散列可能会抛出。

例

二次

#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';
}

二次

产出：

二次

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

二次

另见

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

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http：//en.cppreference.com/w/cpp/Memory/UNIQUE[医]PTR/散列

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