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