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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Forcing exceptions on NANs with GNAT?
Newsgroups: comp.lang.ada
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Date: Thu, 20 Nov 2008 14:46:12 +0100
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Date: 2008-11-20T14:46:12+01:00
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On Thu, 20 Nov 2008 12:09:41 +0100, Markus Schoepflin wrote:

> is it possible to influence the behaviour of GNAT regarding the handling of 
> NANs? (Most importantly in the special case of division by zero.)
> 
> We need to get exceptions whenever a NAN is generated, is this possible 
> somehow? (For example by setting Machine_Overflow to True and recompiling 
> the compiler itself.)

You can scrap IEEE stuff in favor of Ada semantics by declaring your own
floating-point [sub]type with a range specified. The compiler will be
forced to check values:

   type Safe_Float is digits 6 range -10.0E10..+10.0E10;
   
or

   subtype Safe_Float is Float range Float'Range;

then

   X : Safe_Float := 1.0;
   Y : Safe_Float := 0.0;
begin
   Y := X / Y;
exception
   when Error : others =>  -- Should print "range check failed"
      Put_Line (Exception_Message (Error));
end;

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de