60 lines
1.3 KiB
C++
60 lines
1.3 KiB
C++
|
|
// Copyright 2005 Daniel James.
|
|
// Distributed under 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)
|
|
|
|
// Force use of assert.
|
|
#if defined(NDEBUG)
|
|
#undef NDEBUG
|
|
#endif
|
|
|
|
#include <boost/container_hash/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));
|
|
|
|
return 0;
|
|
}
|
|
|