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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 customise boost::hash portably, so that
// it'll work on both compilers that don't implement argument dependent lookup
// and compilers that implement strict two-phase template instantiation.
namespace foo
{
struct custom_type
{
int value;
custom_type(int x) : value(x) {}
#ifndef BOOST_NO_ARGUMENT_DEPENDENT_LOOKUP
friend inline std::size_t hash_value(custom_type x)
{
boost::hash<int> hasher;
return hasher(x.value);
}
#else
std::size_t hash() const
{
boost::hash<int> hasher;
return hasher(value);
}
#endif
};
}
#ifdef BOOST_NO_ARGUMENT_DEPENDENT_LOOKUP
namespace boost
{
std::size_t hash_value(foo::custom_type x)
{
return x.hash();
}
}
#endif
int main()
{
foo::custom_type x(1), y(2), z(1);
boost::hash<foo::custom_type> hasher;
assert(hasher(x) == hasher(x));
assert(hasher(x) != hasher(y));
assert(hasher(x) == hasher(z));
}
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