On Friday, 2 August 2013 12:28:51 UTC+8, CGAT 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; > }
Ouch, is that really what Numbers.equiv is doing? No wonder some of our idiomatic numerical code is so slow - a coercion to BigDecimal is really expensive! It really needs instanceof checks and branches to handle the different cases efficiently. I'll have a go at a ticket/patch that addresses this. -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.