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From: Corey Ashford <yeroca@rocketmail.com>
Subject: Re: Question for the folks who designed Ada95
Date: 1999/04/27
Message-ID: <3725FAD0.917331E4@rocketmail.com>#1/1
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References: <7g2qu4$ca4$1@usenet.rational.com>
 <7g3b5g$p92$1@nnrp1.dejanews.com>
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Date: 1999-04-27T00:00:00+00:00
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Robert Dewar wrote:
> 
> In article <7g2qu4$ca4$1@usenet.rational.com>,
>   "Corey Ashford" <yeroca@rocketmail.com> wrote:
> >
> > The problem with the interfaces package shift
> > operators is that they have fixed types.  So it's
> > difficult to write code for types whose size can vary.
> 
> What we do in GNAT to address this problem is to make the
> shift operators intrinsics. Here is a typical declaration
> from the Interfaces spec:
> 
>    pragma Import (Intrinsic, Shift_Left);
> 
> The nice thing about this approach is that indeed you
> *can* apply this intrinsic to a user defined type. For
> example you can put the following in your code.
> 
>   type My_Modular is mod 2**Integer'Size;
>   function Shift_Left
>      (Value  : My_Modular;
>       Amount : Natural)
>       return   My_Modular;
>   pragma Import (Intrinsic, Shift_Left);
> 
> and this will work fine. Of course this is not guaranteed
> to be portable (perhaps the ARG should look at this one,
> since it is a perfectly legitimate implementation
> decision).
> 

Thanks for the idea!  I'll look into this one.

- Corey