Re: [boost] [parameter] function types as named template parameters?

Subject: Re: [boost] [parameter] function types as named template parameters?
From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2009-01-23 09:39:44

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On Friday 23 January 2009 00:55 am, David Abrahams wrote:
> on Thu Jan 22 2009, Frank Mori Hess <frank.hess-AT-nist.gov> wrote:
> > Does Boost.Parameter support function types as named template type
> > parameters?

>
> Can you post a minimal example that reproduces this bug?  I'm sure
> there's a quick fix.
>

Here you go.  If you undefine NAMED_SIGNATURE_PARAMETER, the test works.  
Otherwise, it fails to compile (I'm using gcc 4.1.2).
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// Copyright Frank Mori Hess 2009.
// Distributed under the Boost Software License, Version
// 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)

#define BOOST_PARAMETER_MAX_ARITY 7

#define NAMED_SIGNATURE_PARAMETER

#include <boost/test/minimal.hpp>
#include <boost/parameter.hpp>

namespace boost
{
  namespace fake_signals2
  {
    template
      <
        typename Signature,
        typename Group = int,
        typename GroupCompare = std::less<Group>
      >
    struct signal
    {};

    namespace keywords
    {
#ifdef NAMED_SIGNATURE_PARAMETER
      BOOST_PARAMETER_TEMPLATE_KEYWORD(signature_type)
#endif
      BOOST_PARAMETER_TEMPLATE_KEYWORD(group_type)
      BOOST_PARAMETER_TEMPLATE_KEYWORD(group_compare_type)
    } // namespace keywords

    template <
#ifdef NAMED_SIGNATURE_PARAMETER
        typename A0,
#else
        typename Signature,
#endif
        typename A1 = parameter::void_,
        typename A2 = parameter::void_
      >
    class signal_type
    {
      typedef parameter::parameters<
#ifdef NAMED_SIGNATURE_PARAMETER
          parameter::required<keywords::tag::signature_type>,
#endif
          parameter::optional<keywords::tag::group_type>,
          parameter::optional<keywords::tag::group_compare_type>
        > parameter_spec;

    public:
      // ArgumentPack
      typedef typename
        parameter_spec::bind<
#ifdef NAMED_SIGNATURE_PARAMETER
        A0,
#endif
        A1, A2>::type
        args;

#ifdef NAMED_SIGNATURE_PARAMETER
      typedef typename parameter::binding<args, keywords::tag::signature_type>::type
        signature_type;
#else
      typedef Signature signature_type;
#endif

      typedef typename
        parameter::binding<args, keywords::tag::group_type, int>::type group_type;

      typedef typename
        parameter::binding<args, keywords::tag::group_compare_type, std::less<group_type> >::type
        group_compare_type;

      typedef signal
        <
          signature_type,
          group_type,
          group_compare_type
        > type;
    };
  } // namespace fake_signals2
} // namespace boost

namespace bs2 = boost::fake_signals2;

int test_main(int, char*[])
{
  {
    using namespace bs2::keywords;
    bs2::signal_type<void ()>::type mysig;
    bs2::signal<void ()> mysig2;
    BOOST_CHECK(typeid(mysig) == typeid(mysig2));
  }

  {
    using namespace bs2::keywords;
    bs2::signal_type<double (int), group_compare_type<std::less<float> > >::type mysig;
    bs2::signal<double (int), int, std::less<float> > mysig2;
    BOOST_CHECK(typeid(mysig) == typeid(mysig2));
  }
  return 0;
}

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