Re: 'withing' problem

["Matthew Heaney" <mheaney@on2.com>]

"Simon Wright" <simon@pushface.org> wrote in message
news:x7vu1vv6b02.fsf@smaug.pushface.org...
> Does your Patient_Forward solution extends to declaring Doctor_Forward
> similarly? I get trouble at
>
>    procedure Visit_Doctor
>      (Patient : in out Patient_Type;
>       Doctor  : in out Root_Doctor'Class) is
>    begin
>       Treat_Patient (Doctor, Patient);
> patients.adb:9:22: expected type "Doctor_Type" defined at doctors.ads:6
> patients.adb:9:22: found type "Root_Doctor'Class" defined at
doctors_forward.ads:3
>    end;

You have to make another renaming declaration, like you did in the Doctor
body:

procedure Visit_Doctor
  (Patient : in out Patient_Type;
   Doctor : in out Root_Doctor'Class) is

   D : Doctor_Type'Class renames Doctor_Type'Class (Doctor);
begin
   Treat_Patient (D, Patient);
end;

You got a compile error because Treat_Patient is not an operation of type
Root_Doctor.  To fix it, you have to downcast from type Root_Doctor'Class to
Doctor_Type'Class.