Re: [boost] [functional] How to avoid a dependency on functional?

Andrzej Krzemienski wrote:

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Is there any recommended way to avoid the functional dependency?

A good question. For the same reason I am reluctant to implement hash support in Boost.Optional.

Optional is easier because you can forward-declare just hash<> and then return empty()? 0: hash<T>()( t_ ). Like shared_ptr.hpp does: // hash_value template< class T > struct hash; template< class T > std::size_t hash_value( boost::shared_ptr<T> const & p ) BOOST_NOEXCEPT { return boost::hash< T* >()( p.get() ); }