Re: array of generic packages?

[Stephen Leake <stephen_leake@acm.org>]

"a malkiel" <malkiel@wannet.net> writes:

> hi im somewhat new to ada. i've been trying to nut this one but can't seem 
> to. Would anyone know if defining an "array of generic packages" is 
> possible? What im looking for is something of the nature:
> 
> type shape_type is (circle, triangle);
> package shapePointer(1) is new shape(circle);
> package shapePointer(2) is new shape(triangle);

This is not directly possible.

But perhaps you are looking for tagged types:

type Shape_Type is tagged abstract limited private;
type Shape_Access_Type is access all Shape_Type;

procedure Draw (Item : in Shape_Type);

type Circle_Type is new Shape_Type with private;

procedure Draw (Item : in Circle_Type);

function New_Circle (Radius : in Float) return Shape_Access_Type;

type Triangle_Type is new Shape_Type with private;

procedure Draw (Item : in Triangle_Type);

function New_Triangle (A, B, C : in Float) return Shape_Access_Type;

Then you can do things like:

type Shape_Array_Type is array (...) of Shape_Access_Type;

My_Shapes : Shape_Array_Type :=
  (New_Circle (2.0),
   New_Triangle (3.0, 4.0, 5.0));


for I in My_Shapes'range loop
   Draw (My_Shapes (I).all);
end loop;


If that's not what you want, perhaps you could say more about what you
do want, and we could talk about how to do it "the Ada way".

-- 
-- Stephe