[Haskell-cafe] Re: instance Eq (a -> b)
Alexander Solla
ajs at 2piix.com
Thu Apr 15 12:02:37 EDT 2010
On Apr 15, 2010, at 12:53 AM, roconnor at theorem.ca wrote:
> I'd call them disrespectful functions, or maybe nowadays I might
> call them
> improper functions. The "good" functions are respectful functions or
> proper functions.
There's no need to put these into a different class. The IEEE defined
this behavior in 1985, in order to help with rounding error. Floats
and doubles are NOT a field, let alone an ordered field. 0.0 =/= -0.0
by design, for floats and doubles. 0.0 == -0.0 for integers, exact
computable reals, etc. The problem isn't the functions, or the Eq
instance. It's the semantics of the underlying data type -- or
equivalently, expecting that floats and doubles form an ordered field.
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