[Haskell-cafe] haskell gsoc proposal for richer numerical type
classes and supporting algorithms
wren ng thornton
wren at freegeek.org
Thu Apr 8 19:58:08 EDT 2010
Gregory Crosswhite wrote:
> On Apr 8, 2010, at 12:25 PM, Casey McCann wrote:
>> Seriously, floating point so-called "numbers" don't even have
>> reflexive equality!
> They don't? I am pretty sure that a floating point number is always equal to itself, with possibly a strange corner case for things like +/- 0 and NaN.
Exactly. NaN /= NaN.
Other than that, I believe that "let x = ... in x == x" is true (because
they are the same bitfield by definition), however it is easy to have
'the same number' without it having the same bitfield representation due
to loss of precision and the like. To say nothing of failures of other
laws leading to overflow, underflow, etc.
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