Re: [Boost-users] [boost-users] Boost.Parameter: ArgumentPack - is type contained

Subject: Re: [Boost-users] [boost-users] Boost.Parameter: ArgumentPack - is type contained
From: Dave Abrahams (dave_at_[hidden])
Date: 2011-03-29 18:29:21

At Tue, 29 Mar 2011 21:22:04 +0200,
Christoph Heindl wrote:
> 
> Hi,
> 
> I'm trying to test an ArgumentPack for containment of a certain
> parameter. Since an ArgumentPack is a valid MPL Sequence, I think
> boost::mpl::contains should do the trick, but I fail to specify the
> correct type. Consider the following
> 
> 
> BOOST_PARAMETER_NAME(color);
> 
> template<class Opts>
> void function_with_opts(const Opts &opts)
> {
>   boost::mpl::contains<Opts, /* what type goes here if I'd like to
> test if color is present in Opts ? */ > ));
> }
> 

try 

  !boost::is_void<
      typename parameter::binding<Opts, tag::color, void>::type
    , void
  >::value

HTH

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com