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From: Mats Weber <matsw@mail.com>
Subject: Re: 11.6
Date: 1999/11/22
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Date: 1999-11-22T13:04:04+00:00
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Matthew Heaney wrote:

>   procedure Push
>     (Stack : in out Stack_Type;
>      Item  : in     Item_Type) is
> 
>      subtype Top_Range is Positive range 1 .. Stack.Size;
> 
>      Top : Natural renames Stack.Top;
>   begin
>      Top := Top_Range'(Top + 1);    --???
>      Stack.Items (Top) := Item;
>   end Push;
> 
> Is it possible, because of 11.6 permissions, that the explicit range
> check in the marked line can be optimized away?
> 
> Another question: if I compile this (or the instantiation?) with checks
> off, then will that cause the explicit range check to be omitted?

Yes, it will. As a rule, I never handle Constraint_Error, but use an if
statement instead in places I know overflow could happen, e.g.

   if Top >= Stack.Size then
      raise Overflow;
   end if;
   Top := Top + 1;