Re: [boost] Boost policy for putting headers in boost/ Was: #3541Support <boost/ptr_map.hpp>

Subject: Re: [boost] Boost policy for putting headers in boost/ Was: #3541Support <boost/ptr_map.hpp>
From: David Abrahams (dave_at_[hidden])
Date: 2009-10-29 16:45:02

on Thu Oct 29 2009, Joel de Guzman <joel-AT-boost-consulting.com> wrote:

>> So +1 for a mpl/type_traits style of organization from me too,
>
> For the record, I am not against this. It is in IMO the logical
> choice for most libraries. What I am saying is that for bigger
> libraries, it is logical to organize in modules. 

As I've been saying, that practice doesn't have to be incompatible with
the  mpl/type_traits style of organization

> When you have
> modules then that flat organization will start to break. E.g.
> if "x.hpp" is a header of module "foo" of library "lib", then,
> the logical structure is:
>
>   boost/
>     lib/
>       foo/
>         a.hpp
>       foo.hpp
>     lib.hpp
>
> Notice that the header for module has the correct header:
>
>     <boost/lib/foo.hpp>

I don't even see x.hpp there.

> However, components of foo (a.hpp) cannot be hoisted outside
> its module. Thus, in this case, this is wrong:
>
>     <boost/lib/a.hpp>
>
> Your example is a prime symptom of the breakage:
> "That said there may be a case to be made for splitting
> into sub-libraries - we did that with Boost.Math to avoid
> confusion between a distribution called X and a special
> function called X.".

> When a library is modular, clashes are typical, e.g.:
>
>   boost/
>     lib/
>       foo/
>         a.hpp
>       bar/
>         a.hpp
>       foo.hpp
>       bar.hpp
>     lib.hpp
>
> So, now you have two headers "a.hpp" under different modules,
> sharing the same name. It then becomes obvious why this is
> wrong:
>
>     <boost/lib/a.hpp>

There are several ways to deal with that.  Aside from renaming one of
the submodules, you could also have boost/lib/a.hpp #include
boost/lib/foo/a.hpp and boost/lib/bar/a.hpp.  It's not aesthetically
ideal, but it's consistent and easier for users.  Those who want to be
more selective can still always reach for boost/lib/bar/a.hpp, for
example.

Have you actually got a name clash situation like that one, BTW?

-- 
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