Re: Access to aliased string declaration question.

[Matthew Heaney <matthew_heaney@acm.org>]

On 10 Jun 1999 04:39, Matthew Heaney <matthew_heaney@acm.org> wrote:

> It's not all that bad, either.  Sometimes you can have it both ways by
> declaring a dynamic (or maybe static) access subtype:
> 
>   type String_Access is access all String;
> 
>   S : aliased String (1 .. 10);
> 
> ...
> 
>   declare
>     subtype S_Access is String_Access (S'Range);
>     SA : S_Access := S'Access;
>   begin
> 
> Here we declare a subtype that points only to strings having the bounds
> of object S.  This is a constrained string object, designed by an access
> object whose (base) type is unconstrained.

Actually, you don't even need the subtype mark:

  declare
    SA : String_Access (S'Range) := S'Access;
  begin


> This works even if the bounds are determined at run-time:
> 
>   procedure Op (F, L : Positive) is
> 
>     S : aliased String (F .. L);
> 
>     subtype S_Access is String_Access (F .. L);  -- or S'Range
> 
>     SA : S_Access := S'Access;
> 
>   begin


No subtype mark is needed here either:

  procedure Op (F, L : Positive) is

     S : aliased String (F .. L);

     SA : String_Access (S'Range) := S'Access;

  begin