Re: [boost] hash_fwd dependency

Subject: Re: [boost] hash_fwd dependency
From: Peter Dimov (lists_at_[hidden])
Date: 2014-06-08 07:33:09

Daniel James wrote:
> On 7 June 2014 17:41, Peter Dimov <lists_at_[hidden]> wrote:
> > While the general subject of forwarding headers still deserves 
> > consideration, in this specific case I wonder if moving funcional/hash 
> > into its own 'hash' module would not alleviate most of the problem.
>
> The point of the forwarding header was to be a lightweight header, because 
> the main header is quite heavy, so separating out the forwarding header is 
> probably the right thing to do.

It's definitely the right thing to do.

This doesn't mean that splitting 'hash' into its own module isn't also the 
right thing to do.

That's what modularization means - to isolate independent components. 'hash' 
is completely independent of the rest of the functional library, it's even 
of a different kind.

> Looking at your report, many of functional's dependencies seem to be 
> caused by problems elsewhere, e.g. boost/functional/factory.hpp includes 
> boost/pointee.hpp from iterator, which pulls in a lot of modules. I think 
> the problem there is with boost/pointee.hpp.

boost/pointee.hpp, along with boost/indirect_reference.hpp and 
boost/detail/is_incrementable.hpp, are an obvious target, one that I've 
already identified. If you look at them, however, you'll see that they can't 
go to Core in their present form, as they have dependencies on MPL and 
TypeTraits. They will be dealt with, in due time.

At the moment, I've been concentrating on (a) low-hanging fruits that (b) 
don't have potential to break code. 'pointee' and friends are neither. 
Splitting 'hash' into its own module is both. Separating hash_fwd could be, 
if we figure out where to put it, which I estimate will take time.