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// Copyright Daniel James 2005. Use, modification, and distribution are
// subject to the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#include <boost/functional/hash.hpp>
#include <cassert>
// This example illustrates how to use boost::hash_combine to generate a hash
// value from the different members of a class. For full details see the hash
// tutorial.
class point
{
int x;
int y;
public:
point() : x(0), y(0) {}
point(int x, int y) : x(x), y(y) {}
bool operator==(point const& other) const
{
return x == other.x && y == other.y;
}
friend std::size_t hash_value(point const& p)
{
std::size_t seed = 0;
boost::hash_combine(seed, p.x);
boost::hash_combine(seed, p.y);
return seed;
}
};
int main()
{
boost::hash<point> point_hasher;
point p1(0, 0);
point p2(1, 2);
point p3(4, 1);
point p4 = p1;
assert(point_hasher(p1) == point_hasher(p4));
// These tests could legally fail, but if they did it'd be a pretty bad
// hash function.
assert(point_hasher(p1) != point_hasher(p2));
assert(point_hasher(p1) != point_hasher(p3));
}
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