[Boost-users] Overloading boost::hash_value GCC

Subject: [Boost-users] Overloading boost::hash_value GCC
From: André Santee (andre.santee_at_[hidden])
Date: 2011-07-01 17:48:48

I'm having a hard time trying to compile my code here. What I'm doing is to
overload the boost::hash_value function to use boost::unordered_map with a
custom Vector2 class.

My code:

// Vector2 hash function
namespace boost {
inline std::size_t hash_value(Vector2 const& p)
{
    std::size_t seed = 0;
    boost::hash_combine(seed, p.x);
    boost::hash_combine(seed, p.y);
    return seed;
}
} // namepace boost

boost::unordered_map<Vector2, EntityList, boost::hash<Vector2> >
buckets;[/code]

It compiles and run fine on msvc 9.0 but gcc says the function does not
exist (it looks like to me that it does exist!).

error message:
Compile++ thumb  : Application <= BucketManager.cpp
In file included from /boost/functional/hash/hash.hpp:510,
                 from /boost/functional/hash.hpp:6,
                 from /boost/unordered/unordered_map.hpp:17,
                 from BucketManager.h:35,
                 from BucketManager.cpp:24:
/boost/functional/hash/extensions.hpp: In member function 'size_t
boost::hash<T>::operator()(const T&) const [with T = math::Vector2]':
/boost/unordered/detail/unique.hpp:183:   instantiated from 'typename
boost::unordered_detail::hash_unique_table<T>::value_type&
boost::unordered_detail::hash_unique_table<T>::operator[](const typename
T::key_type&) [with T = boost::unordered_detail::map<math::Vector2,
boost::hash<math::Vector2>, std::equal_to<math::Vector2>,
std::allocator<std::pair<const math::Vector2, std::list<RenderEntity*> > >
>]'
/boost/unordered/unordered_map.hpp:406:   instantiated from 'T&
boost::unordered_map<K, T, H, P, A>::operator[](const K&) [with K =
math::Vector2, T = std::list<RenderEntity*>, H = boost::hash<math::Vector2>,
P = std::equal_to<math::Vector2>, A = std::allocator<std::pair<const
math::Vector2, std::list<RenderEntity*> > >]'
BucketManager.cpp:128:   instantiated from here
/boost/functional/hash/extensions.hpp:176: error: no matching function for
call to 'hash_value(const math::Vector2&)'
/boost/functional/hash/hash.hpp:136: note: candidates are: size_t
boost::hash_value(bool)
/boost/functional/hash/hash.hpp:141: note:
             size_t boost::hash_value(char)
/boost/functional/hash/hash.hpp:146: note:
             size_t boost::hash_value(unsigned char)
/boost/functional/hash/hash.hpp:151: note:
             size_t boost::hash_value(signed char)
/boost/functional/hash/hash.hpp:156: note:
             size_t boost::hash_value(short int)
/boost/functional/hash/hash.hpp:161: note:
             size_t boost::hash_value(short unsigned int)
/boost/functional/hash/hash.hpp:166: note:
             size_t boost::hash_value(int)
/boost/functional/hash/hash.hpp:171: note:
             size_t boost::hash_value(unsigned int)
/boost/functional/hash/hash.hpp:176: note:
             size_t boost::hash_value(long int)
/boost/functional/hash/hash.hpp:181: note:
             size_t boost::hash_value(long unsigned int)
/boost/functional/hash/hash.hpp:187: note:
             size_t boost::hash_value(wchar_t)
/boost/functional/hash/hash.hpp:194: note:
             size_t boost::hash_value(boost::long_long_type)
/boost/functional/hash/hash.hpp:199: note:
             size_t boost::hash_value(boost::ulong_long_type)
/boost/functional/hash/hash.hpp:313: note:
             size_t boost::hash_value(float)
/boost/functional/hash/hash.hpp:318: note:
             size_t boost::hash_value(double)
/boost/functional/hash/hash.hpp:323: note:
             size_t boost::hash_value(long double)
make: ***
-- 
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