hash-class.md

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hash Class | Microsoft Docs		11/04/2016			cpp-standard-libraries		article	functional/std::hash bitset/std::hash memory/std::hash string/std::hash system_error/std::hash thread/std::hash typeindex/std::hash vector/std::hash XSTDDEF/std::hash xstring/std::hash	C++	std::hash [C++] std::hash [C++] std::hash [C++] std::hash [C++] std::hash [C++] std::hash [C++] std::hash [C++] std::hash [C++] std::hash [C++]	e1b500c6-a5c8-4f6f-ad33-7ec52eb8e2e4	21	corob-msft	corob	ghogen

hash Class

Computes hash code for a value.

Syntax

template <class Ty>  
struct hash {  
    size_t operator()(Ty val) const; 
};  

Remarks

The function object defines a hash function, suitable for mapping values of type Ty to a distribution of index values. The member operator() returns a hash code for val, suitable for use with template classes unordered_map, unordered_multimap, unordered_set, and unordered_multiset. The standard library provides specializations for basic types: Ty may be any scalar type, including pointer types and enumeration types. In addition, there are specializations for the library types string, wstring, u16string, u32string, string_view, wstring_view, u16string_view, u32string_view, bitset, error_code, error_condition, optional, shared_ptr, thread, type_index, unique_ptr, variant, and vector<bool>.

Example

// std__functional__hash.cpp   
// compile with: /EHsc   
#include <functional>   
#include <iostream>   
#include <unordered_set>   
  
int main()   
    {   
    std::unordered_set<int, std::hash<int> > c0;   
    c0.insert(3);   
    std::cout << *c0.find(3) << std::endl;   
  
    return (0);   
    }  
  

3  

Requirements

Header: <functional>

Namespace: std

See Also

<unordered_map>
unordered_multimap Class
unordered_multiset Class
<unordered_set>