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From: "Stephen Colebourne" <scolebourne@btopenworld.com>
To: "Jakarta Commons Developers List" <commons-dev@jakarta.apache.org>
References: <Pine.GSO.4.58.0405281302100.3242@catfish.csail.mit.edu>
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Subject: Re: [lang] [math] org.apache.commons.lang.math.Fraction class
Date: Sun, 30 May 2004 22:54:25 +0100
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> > The existing add(), subtract(), and multiplyBy() and divide() code (as
far
> > as I can tell) all returned reduced fractions, so existing arithmetic
code
> > should largely be unaffected.  The primary visible difference is that
> > before
> >  Fraction.getFraction(2,4).equals(Fraction.getFraction(1,2))==false
> > and now it would be true.
> > I view the previous behavior as "surprising" and a bug, honestly.
>
> I am inclined to agree here; though I am not sure exactly what the
> original author's intention was and how people may be using the class now.
>    The fact that the arithmetic operations return reduced fractions makes
> it hard to understand why equals works the way that it does now.

What about getNumerator()/getDenominator() - won't these change if 2/4 is
held differently? I believe that we need to preserve the 2/4 concept
distinct from 1/2, at least in the [lang] version.


> One thing that we might want to consider, given the magnitude of the
> changes, is deprecating this in [lang] and moving it to [math].  That way,
> among other things, the (better) continued fraction implementation in
> [math] could be used in getFraction(double).  The improved gcd and checked
> integer arithmetic methods in the patch might also make good additions to
> o.a.c.math.MathUtils.

The [lang] code needs to work and be reliable. However I suspect that a
[math] version and [lang] version may be appropriate with slightly different
semantics.

Stephen


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