Re: [boost] [placeholders]

Subject: Re: [boost] [placeholders]
From: Joel de Guzman (joel_at_[hidden])
Date: 2010-07-27 21:05:07

On 7/27/2010 11:41 PM, Andrzej Krzemienski wrote:
> Hi,
> I have a problem with Boost.Bind placeholders. Namely, once I include
> the<boost/bind.hpp>  it automatically brings placeholders _1, _2, ..
> into scope and I cannot use placeholders from other libraries like
> Spirit.Qi any more. I.e. I can but I need to qualify them like qi::_1,
> qi::_2, which is annoying. I include<boost/bind.hpp>  in a precompiled
> header, so I have no option of not including it.
> Boost.Bind could define them in namespace boost::bind_placeholders and
> we could control their visibility with namespace using directive. This
> is what Spirit does, and it is cute. I guess I would not be able to
> convince anyone that Bind should do the same.
> But would it be possible to define placeholders _1, _2, ... as
> something more generic in Boost, unrelated to any particular library?
> Then boost::bind, would treat it as its own placeholders, Spirit
> semantic actions would treat them as its own placeholders, but they
> would be exactly same placeholders.

Yes, it is possible. That is what we are trying to solve with the
Phoenix-3 project: unification of all placeholders.

Regards,
-- 
Joel de Guzman
http://www.boostpro.com
http://spirit.sf.net