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Date: Sat, 19 Oct 2013 07:30:05 -0700 (PDT)
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Subject: Re: Possible GNAT problem with aliased parameters.
From: sbelmont700@gmail.com
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Date: 2013-10-19T07:30:05-07:00
List-Id: <comp.lang.ada>

On Saturday, October 19, 2013 1:48:58 AM UTC-4, Shark8 wrote:
> now I'm trying to figure a way to do it

The only way would be to hack it together with access discriminants:

type Maze (n : access Maze'Class;
           s : access Maze'Class;
           e : access Maze'Class;
           w : access Maze'Class) is tagged null record;=20
       =20
function Create (North, South, East, West : aliased in out Maze'Class:=3D N=
one) return Maze is
begin
   if Just_North then
      return Maze'(n =3D> North'Access, null, null, null);
   elsif North_And_South then
      return Maze'(n =3D> North'Access, South'Access, null, null);
  =20
   -- continue a bunch more times for all possibilities
  =20
   end if;

end Create;
  =20
This is a shame, because the aliased parameter/access discriminant method w=
orks so well for simple composition of one object, and extending it to arra=
ys of objects would eliminate what is essentially the last unnecessary use =
of access types (I bemoaned the inability to pass around arrays of local ac=
cess types awhile back in another thread, and this is another good example =
of why).

-sb