forked from boostorg/container_hash
57 lines
1.3 KiB
C++
57 lines
1.3 KiB
C++
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// Copyright Daniel James 2005. Use, modification, and distribution are
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// subject to 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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#include <boost/functional/hash.hpp>
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#include <cassert>
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// This example illustrates how to customise boost::hash portably, so that
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// it'll work on both compilers that don't implement argument dependent lookup
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// and compilers that implement strict two-phase template instantiation.
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namespace foo
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{
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struct custom_type
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{
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int value;
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custom_type(int x) : value(x) {}
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#ifndef BOOST_NO_ARGUMENT_DEPENDENT_LOOKUP
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friend inline std::size_t hash_value(custom_type x)
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{
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boost::hash<int> hasher;
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return hasher(x.value);
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}
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#else
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std::size_t hash() const
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{
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boost::hash<int> hasher;
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return hasher(value);
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}
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#endif
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};
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}
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#ifdef BOOST_NO_ARGUMENT_DEPENDENT_LOOKUP
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namespace boost
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{
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std::size_t hash_value(foo::custom_type x)
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{
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return x.hash();
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}
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}
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#endif
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int main()
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{
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foo::custom_type x(1), y(2), z(1);
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boost::hash<foo::custom_type> hasher;
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assert(hasher(x) == hasher(x));
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assert(hasher(x) != hasher(y));
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assert(hasher(x) == hasher(z));
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}
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