//Purpose:
//  Prototype d version of boost::mpl::set
//
//{ChangeLog:
//  2007-01-09.0622
//    WHAT:
//      Changed has_key.tester according to 
//      suggestion in post with headers:
/*
From: Daniel Keep <daniel.keep+lists@gmail.com>
Newsgroups: digitalmars.D
Subject: Re: can't use variadic template arg in dependent type
Date: Tue, 09 Jan 2007 17:15:49 +0800
 */
//}ChangeLog:
  class
bool_
  ( bool TrueFalse
  )
{
}
  class
set
  (
  )
{
}
  class
set
  ( Head
  , Tail...
  )
  : set!(Tail) //needed if specialization of has_key_tester to work.
{
    private static alias Head _Head; 
    private static alias Tail _Tail; 
}
  
  template
has_key
  ( Key
  )
{
      bool_!(true) 
    tester
      ( Set
      )
      ( Set a_set
      )
    {
        alias Set._Head Head;
        alias Set._Tail Tail;
        static if( !is( set!(Head,Tail) == Set) )
        static assert(false, "I can see through your clever deception!");
        return new bool_!(true);
    }
      bool_!(false) 
    tester
      ( NotSet
      )
      ( ...
      )
    {
        return new bool_!(false);
    }
}

  class 
not_member
{}

  bool_!(true)
tester
  ( Set
  )
  ( Set a_set
  )
{
    alias Set._Head Head;
    alias Set._Tail Tail;
    static if( !is( set!(Head,Tail) == Set) )
    static assert(false, "I can see through your clever deception!");
    return new bool_!(true);
}
  
void test()
{
    auto set_int_float=new set!(int,float);
    {
        bool_!(true) result=tester(set_int_float);
    }
    auto set_empty=new set!();
    set_empty=set_int_float;//check that set_empty is superset of set_int_float
    {
        bool_!(true) result=has_key!(int).tester(set_int_float);
    }
    {
        bool_!(false) result=has_key!(not_member).tester(set_empty);
    }
    {
        bool_!(false) result=has_key!(not_member).tester(set_int_float);
    }
}