I agree, which is why I wrote a patch for the ticket
http://dev.clojure.org/jira/browse/CLJ-1118
(Depending on when you read this, dev.clojure.org may not be accessible due
to a recent DNS update made by the Clojure folks. Wait a while and try
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It makes not only the change you suggest, but also another one to how hash
is calculated for BigDecimal values, so that hash is still consistent with
=. Take a look at it and see if you think it is correct.
Andy
On Thu, Aug 1, 2013 at 9:28 PM, CGAT <genovese...@gmail.com> wrote:
> My understanding of == is that it is intended to establish numerical
> equivalence
> across types. But I think that basic contract fails with BigDecimal. For
> instance,
>
> (== 1M 1.0M) ; => false
>
> because the scale properties of these numbers are different. So then of
> course:
>
> [(== 1 1N 1.0) (== 1 1N 1.0 1M) (== 1 1N 1.0 1.0M) (== 1 1.0 1N 1.0M)]
> ; => [true true true false]
> and
> [(== 1.0M 1.0) (== 1.0 1) (== 1 1N) (== 1N 1.0M)]
> ; => [true true true false]
>
> I find your lack of transitivity (and commutativity) ... disturbing.
>
> The issue is that there are two notions of equality for BigDecimal,
> equals and compareTo, where equals compares value *and* scale while
> compareTo compares numerically.
>
> The other numeric types use equals for equivalence, quite reasonably.
> But in class BigDecimalOps in clojure/lang/Numbers.java, I propose
> that
>
> public boolean equiv(Number x, Number y){
> return toBigDecimal(x).equals(toBigDecimal(y));
> }
>
> should be
>
> public boolean equiv(Number x, Number y){
> return toBigDecimal(x).compareTo(toBigDecimal(y)) == 0;
> }
>
> to give the proper sense of equivalence.
>
> I haven't had a chance yet to recompile with this change to test it,
> but we do have
>
> (zero? (. 1.0M (compareTo 1M))) ; => true
> (zero? (. 1.0000M (compareTo 1M))) ; => true
> (zero? (. 1.000M (compareTo 1.0M))) ; => true
>
> as desired.
>
> Reactions?
>
> Best,
>
> Chris
>
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