Re: Question: Combination of Access and Constraining

[Dmitry A. Kazakov <mailbox@dmitry-kazakov.de>]

On 20 Feb 2003 00:06:15 -0800, papand0pul0@yahoo.com (Papandopulo)
wrote:

>Small Ada question:
>
>I need one function to accept
>an array of unknown size of Boolean,
>so I declare type and function:
>
>type Tp is array (Positive range <>) of Boolean;
>type Tp_Access is access all Tp;
>
>function Fn (Arg : in Tp_Access) return Natural;

Pointers are inherently bad. Why not:

function Fn (Arg : Tp) return Natural;

>Now I try to call it with the constrained array:
>
>declare
>  type TpCon is new Tp(1..1);
                       ^^^^^^
But this is another type! Probably you meant a subtype:

subtype TpCon is Tp(1..1);

>  Arr : aliased TpCon;
>begin
>  Arr(1) := True;
>  Res := Fn (Arr'Access);
>end;
>
>Compiler says on the invocation line:
>expected type: Tp_Access defined at ...
>found type TpCon defined at ...
>
>I think that access to constrained
>type should be convertible to access
>to unconstrained type.
>
>So where I am going wrong here ?

You are mixing types and subtypes. If you want just to put a
constraint on a type, declare a constrained subtype.

---
Regards,
Dmitry Kazakov
www.dmitry-kazakov.de