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Subject: Re: Teaching new tricks to an old dog (C++ -->Ada)
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From: Pascal Obry <pascal@obry.org>
Date: 09 Mar 2005 18:40:47 +0100
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Date: 2005-03-09T18:40:48+01:00
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Hyman Rosen <hyrosen@mail.com> writes:

> Keeping in mind that all template instantiations in C++
> are static and done at compile time, the answer is yes.
> Here's a little example.

Hard to understand. This looks like a template which instanciate other
templates. No recusive definitions here.

>      #include <typeinfo>
>      #include <iostream>
>      #include <ostream>
> 
>      struct NIL { };

   type Nil is null record;

>      template <typename HEAD, typename TAIL> struct CONS { };

   generic
      type HEAD is private;
      type TAIL is private;
   package CONS_PKG is

      type CONS is null record;

   end CONS_PKG;


>      template <typename T> struct x;

   generic
      type T is private;
   package X_PKG is

      type X is null record;

   end X_PKG;

>      template <> struct x<NIL> { static void f() { } };

   generic
   package X_NIL_PKG is 
      type X_NIL is new X_PKG (Nil);

      procedure f;

   end X_NIL_PKG;

>      template <typename HEAD, typename TAIL> struct x< CONS<HEAD,TAIL> >
>      {
>          static void f()
>          {
>              std::cout << typeid(HEAD).name() << "\n";
>              x<TAIL>::f();
>          }
>      };

   generic
      type HEAD is private;
      type TAIL is private;
   package X_CON_PKG is 

      package CONS_HT is new CONS_PKG (HEAD, TAIL);

      package X_CONS is new X_PKG (CONS_HT.CONS);

      procedure F;

   end X_NIL_PKG;


>      int main()
>      {
>          x< CONS<int, CONS<int, CONS<double, CONS<char, NIL> > > > >::f();
>      }

My C++ is a bit rusty, let me know if I got something wrong...

Pascal.

-- 

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