//cross(or cartesian) product of sequence of domains.
//  (C) Copyright Larry Evans 2010.
//
//  Permission to copy, use, modify, sell and distribute this software
//  is granted provided this copyright notice appears in all copies.
//  This software is provided "as is" without express or implied
//  warranty, and with no claim as to its suitability for any purpose.
//
#ifndef BOOST_MPL_CROSS_PRODUCT_HPP_INCLUDED
#define BOOST_MPL_CROSS_PRODUCT_HPP_INCLUDED
#include <boost/mpl/package.hpp>
#include <boost/mpl/push_back.hpp>
#include <boost/mpl/join_pack.hpp>
#include <boost/mpl/arg.hpp>
#include <boost/mpl/fold_assoc_seq.hpp>
#include <boost/mpl/outer_product_pack.hpp>

namespace boost
{
namespace mpl
{
namespace detail
{
namespace _cross_product_pack
{
  template
  < template<typename,typename>class Push=mpl::push_back
  >
struct cross_many_one
{
      template
      < typename Many
      , typename One
      >
    struct apply
    {
            typedef
          typename outer_product_pack
          < Push<arg<1>,arg<2> >
          >::template apply<Many,One>::type
        cross_nested
        ;
            typedef
          typename fold_assoc_seq
          < assoc_left
          , join_pack<arg<1>,arg<2> >
          , package<>
          , cross_nested
          >::type
        type
        //Given:
        //  cross_nested = 
        //    package
        //    < package<e1_1, e1_2, ... , e1_n[1]>
        //    , package<e2_1, e2_2, ... , e1_n[2]>
        //
        //    .
        //    .
        //    .
        //
        //    , package<em_1, em_2, ... , em_n[m]>
        //    >
        //Produces "flattened" version of cross_nested:
        //  type =
        //    package
        //    < e1_1, e1_2, ... , e1_n[1]
        //    , e2_1, e2_2, ... , e2_n[2]
        //
        //    .
        //    .
        //    .
        //
        //    , em_1, em_2, ... , em_n[m]
        //    >
        ;
    
    };//template apply
};
}//exit _cross_product_pack namespace
}//exit detail namespace
  template
  < typename domains
  , template<typename,typename>class Push=push_back
  >
struct cross_product_pack
;
  template
  < typename... domains
  , template<typename,typename>class Push
  >
struct cross_product_pack
  < package<domains...>
  , Push
  >
{
        typedef
      typename fold_assoc_seq
      < assoc_left
      , detail::_cross_product_pack::cross_many_one<Push>
      , package<package<> >
      , package<domains...>
      >::type
    type
    ;
};

}//exit mpl namespace
}//exit boost namespace
#endif