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From: eachus@roadkill.mitre.org (Robert I. Eachus)
Subject: Re: Integer truncation and other recipes
Date: 1996/06/05
Message-ID: <EACHUS.96Jun5184212@roadkill.mitre.org>#1/1
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distribution: world
references: <4nv3tmINNql5@oasys.dt.navy.mil> <JSA.96May22221027@organon.com>
organization: The Mitre Corp., Bedford, MA.
newsgroups: comp.lang.ada
Date: 1996-06-05T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <4p4atg$tc5@watnews1.watson.ibm.com> ncohen@watson.ibm.com (Norman H. Cohen) writes:

  > Not a very satisfying answer.  Suppose you want to delay until the next
  > time the minute hand sweeps past the 12.  It would be nice to be able to
  > write...

  > Duration(Float'Floor(Float(Now)/60.0)) is a poor substitute for
  > Duration'Floor(Now/60.0).

  > I think the failure to generalize certain of the floating-point
  > attributes to fixed-point types was an unfortunate oversight.

   Agreed.  In fact on some implementations:

   60.0 * Duration(Integer(Now/Duration'SMALL)/
               (60*Integer(1.0/Duration'SMALL)))

   Is the only reasonable way to do this due to accuracy issues.
However, that approach depends on (in Ada 83) the UI which says that
1.0 is a model number of Duration.  If fact I have had to replace the
divisions by Duration'SMALL by Unchecked_Conversion with some
compilers that simply do not recognize this idiom.  (The problem is
not that they do a divide, it's that they do a divide which
overflows...) 


--

					Robert I. Eachus

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