[Boost-users] result_of protocol

Subject: [Boost-users] result_of protocol
From: Hicham Mouline (hicham_at_[hidden])
Date: 2010-02-26 04:40:25

Hello,

I get the following msvc2008 error:

error C2825: 'Holder': must be a class or namespace when followed by '::'

in the following code

----------------------------------------------------------------------------------
struct extract_rule {

  template <typename Sig> struct result;

  template <typename Holder>
  struct result< extract_rule(const Holder) > {
    typedef const typename Holder::type& type;
  };

  template <typename Holder>
  typename result< extract_rule(const Holder) >::type
  operator()( const Holder& h ) const
  {
    return h.rule;
  }
};
----------------------------------------------------------------------------------

1>        with
1>        [
1>            Sig=extract_rule (const onevariantrule<parameters_t,0,boost::spirit::istream_iterator> )
1>        ]

The template onevariantrule<> is defined _before_ extract_rule.

-------------------------------------------------------------------------------------------
template <typename parameters_t, unsigned n, typename Iterator> 
struct onevariantrule {
  typedef .... type;
};
-------------------------------------------------------------------------------------------

Holder matches onevariantrule<parameters_t,0,boost::spirit::istream_iterator>.
That template instantiation is indeed a class.
It has the inner field called "type".

Any ideas would be appreciated,