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From: Keith Thompson <kst@cts.com>
Subject: Re: Ada and Java. different behaviour. casting long to int problem.
Date: 1999/06/23
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Date: 1999-06-23T21:31:28+00:00
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Marin David Condic <condicma@bogon.pwfl.com> writes:
[...]
> If I understand you correctly, the answer is "yes". In Ada, it would
> look sort of like this:
> 
> X : Integer := Integer'Last ; --  Contains max value for type integer.
> 
> ...
> 
> X := X + 1 ; --  No overflow - X contains Integer'Last

Out of curiosity, would it generally be more useful for saturation to
be "sticky", like IEEE infinity?

For example, with non-sticky saturation, you might get something like
this:

   X : Integer := Integer'Last;
   ...
   X := X * 10;		-- saturation, X = Integer'Last
   X := X / 10;		-- X = Integer'Last / 10

On the other hand, an infinite value in IEEE floating point is not
just a large number; infinity / 10 = infinity.

I suspect the answer depends on the application, and on what kind of
further calculations you want to do on saturated results.  Making
saturation sticky would require reserving certain bit patterns in an
integer type, which would cause some run-time overhead on all
operations on that type.  It would also make conversions between a
saturating type and an equivalent non-saturating type a little tricky.

-- 
Keith Thompson (The_Other_Keith) kst@cts.com  <http://www.ghoti.net/~kst>
San Diego Supercomputer Center  <http://www.sdsc.edu>                 <*>
One of the great tragedies of ancient history is that Helen of Troy
lived before the invention of the champagne bottle.