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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: Renaming Fixed Point Mutiplicative operator in Ada 95
Date: 1998/05/20
Message-ID: <dewar.895707841@merv>#1/1
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References: <3561F32B.2F0B@innotts.co.uk>
 <matthew_heaney-ya023680001905982254370001@news.ni.net>
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Newsgroups: comp.lang.ada
Date: 1998-05-20T00:00:00+00:00
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Matthew says

<<(start of quote)
   function MultFixed (LEFT : NewFixed; RIGHT : NewFixed) return
NewFixed ;
(end of quote)

This is a very misguided thing to do.  Please, do not do this.
>>


What is misguided here is Matthew's entirely odd view about defining
your own operators for fixed-point. Of *course* you may want to do this
for many good reasons, one of which was alluded to in the original
question (another good reason would be to provide modular fixed-point).

The fact that Ada 95 has introduced a nasty incompatibility here is
very irritating. In practice this is one of the really nasty upward
non-compatibilities, and often there is no very simple fix that does
not involve lots of changes to a program.

THe abstraction model of Ada depends on the idea of being able to
override the predefined stuff in a uniform manner. The fact that
you can easily and clearly define "*" on all types except fixed-point
types is definitely a non-orthogonal irritation.

Of course this should not for a moment suggest the extreme reaction of
the original poster, who seems to think that this is a bar to the use
of fixed-point. There are a number of perfectly straightforward alternative
ways to solve the problem. The most irritating case is existing legacy
code, since of course the quoted original program was legal in Ada 83.