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

Subject: Re: [boost] [functional] How to avoid a dependency on functional?
From: Peter Dimov (lists_at_[hidden])
Date: 2015-01-09 15:30:45

> Beman Dawes wrote:
> > Filesystem has a dependency on <boost/functional/hash_fwd.hpp> in order 
> > to supply this:
> >
> >   inline std::size_t hash_value(const path& x)
> >   {
> > # ifdef BOOST_WINDOWS_API
> >     std::size_t seed = 0;
> >     for(const path::value_type* it = x.c_str(); *it; ++it)
> >       hash_combine(seed, *it == '/' ? L'\\' : *it);
> >     return seed;
> > # else   // BOOST_POSIX_API
> >     return hash_range(x.native().begin(), x.native().end());
> > # endif
> >   }
> ...
> > Is there any recommended way to avoid the functional dependency?
>
> In this specific case, I would forward-declare hash_combine and 
> hash_range.

There is also the option of just returning hash_value( x.native() ). This 
would require a forward declaration of hash_value for string.