problem with polymorphism

problem with polymorphism

[Henri Delebecque]

Hello,

I'm currently evaluating tagged types in Ada95, and encounter some
problems
with the following code:

type Point is tagged record
        x : integer := 0;
        y : integer := 0;
end record;
type Point3D is new Point with record
        z : integer := 0;
end record;
procedure print (unPoint : in Point) is
begin
        put ("Point:[");
	...
end print;
procedure print (unPoint3D : in Point3D) is
begin
...
end print;
procedure printing (unPoint : in Point'Class) is
begin
        print(unPoint);
end printing;

gnat's error message is
testpoly.adb:40:17: class-wide argument not allowed here
testpoly.adb:40:17: "imprime" is not a primitive operation of "Point"

Please, could someone helps me ?
Thanks
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| Henri Delebecque                        delebecq@supelec.fr |
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Re: problem with polymorphism

[Jon S Anthony]

Henri Delebecque <delebecq@supelec.fr> writes:

> gnat's error message is
> testpoly.adb:40:17: class-wide argument not allowed here
> testpoly.adb:40:17: "imprime" is not a primitive operation of "Point"

Insufficient information.  "imprime" is not in your code snippet and
it is clearly the problem based on the explicit error message...


/Jon

-- 
Jon Anthony
Synquiry Technologies, Ltd., Belmont, MA 02178, 617.484.3383
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 Who'd notice?"  -- Londo Mollari