STL - Unorderedset - 自定义哈希函数

1. hash工具类

hashval.hpp

#ifndef _Core_HashVal_H_

#define _Core_HashVal_H_

#include <functional>

// from boost (functional/hash):

// see http://www.boost.org/doc/libs/1_35_0/doc/html/hash/combine.html

template <typename T>

inline void hash_combine (std::size_t& seed, const T& val)

{

    seed ^= std::hash<T>()(val) + 0x9e3779b9 + (seed<<) + (seed>>);

}

// auxiliary generic functions to create a hash value using a seed

template <typename T>

inline void hash_val (std::size_t& seed, const T& val)

{

    hash_combine(seed,val);

}

template <typename T, typename... Types>

inline void hash_val (std::size_t& seed,

                      const T& val, const Types&... args)

{

    hash_combine(seed,val);

    hash_val(seed,args...);

}

// auxiliary generic function to create a hash value out of a heterogeneous list of arguments

template <typename... Types>

inline std::size_t hash_val (const Types&... args)

{

    std::size_t seed = ;

    hash_val (seed, args...);

    return seed;

}

#endif

2. UnorderedSetTest.cpp

#include <unordered_set>

#include "../../Core/print.hpp"

#include "UnorderedSetTest.h"

#include "../../Core/hashval.hpp"

#include "../../Domain/Models/Customer.h"

#include "../../Domain/Models/CustomerHash.h"

#include "../../Domain/Models/CustomerEqual.h"

#include <string>

#include <iostream>

using namespace std;

void UnorderedSetTest::simpleHashFunc()

{

    // unordered set with own hash function and equivalence criterion

    unordered_set<Customer, CustomerHash, CustomerEqual> custset;

    custset.insert(Customer("arne", "wink", ));

    custset.insert(Customer("peter", "zhang", ));

    PRINT_ELEMENTS(custset);

    Customer cust = Customer("arne", "wink", );

    if (custset.find(cust) != custset.end())

    {

        cout << "Customer: " << cust << " found!" << endl;

    }

    else

    {

        cout << "Customer: " << cust << " not exists!" << endl;

    }

    Customer cust2 = Customer("arne", "wink2", );

    if (custset.find(cust2) != custset.end())

    {

        cout << "Customer: " << cust2 << " found!" << endl;

    }

    else

    {

        cout << "Customer: " << cust2 << " not exists!" << endl;

    }

}

void UnorderedSetTest::run()

{

    printStart("simpleHashFunc()");

    simpleHashFunc();

    printEnd("simpleHashFunc()");

}

3. 运行结果:

---------------- simpleHashFunc(): Run Start ----------------
[arne,wink,70] [peter,zhang,70]
Customer: [arne,wink,70] found!
Customer: [arne,wink2,70] not exists!
---------------- simpleHashFunc(): Run End ----------------