If you can't stomach the weirdness of floating point then perhaps you should try to define your own type that obeys all the expected laws? :)
On Jan 11, 2008 3:36 AM, Wolfgang Jeltsch <[EMAIL PROTECTED]> wrote: > Am Freitag, 11. Januar 2008 11:03 schrieb Felipe Lessa: > > Another thing for the record: Goldberg says > > > > "The introduction of NaNs can be confusing, because a NaN is never > > equal to any other number (including another NaN), so x = x is no > > longer always true. In fact, the expression x /= x is the simplest way > > to test for a NaN if the IEEE recommended function Isnan is not > > provided. Furthermore, NaNs are unordered with respect to all other > > numbers, so x <= y cannot be defined as not x > y. Since the > > introduction of NaNs causes floating-point numbers to become partially > > ordered, a compare function that returns one of <, =, >, or unordered > > can make it easier for the programmer to deal with comparisons." > > > > Goldberg, David. What Every Computer Scientist Should Know About > > Floating-Point Arithmetic. > > http://docs.sun.com/source/806-3568/ncg_goldberg.html . > > > > As GNU is not Unix, NaN is not a number, so what is standard about > > numbers doesn't work for them. I don't think there's a compeling > > reason about changing this behavior, specially because it's what's > > specified in the IEEE 754. > > There is a really compelling reason: If the order on floating point > numbers is > partial then there is no meaningful Ord instance for them. > > And what do Hugs and GHCi say? Their answers are plain horror: > > Hugs, version 20050308: > > compare (0 / 0) (0 / 0) => EQ > > 0 / 0 == 0 / 0 => False > > GHCi 6.8.2: > > compare (0 / 0) (0 / 0) => GT > > 0 / 0 > 0 / 0 => False > > Anyone interested in filing bug reports? > > > […] > > Best wishes, > Wolfgang > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
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