[Haskell-cafe] A question about "monad laws"

[Dan Weston]

Not to be picky, but where did you hear that (==) established an 
equivalence relation? Not I expect from the Haskell98 Report!

The only law I can find there is that

   x /= y iff not (x == y)

So, the definition  x == y = False
                     x /= y = True

would be perfectly legitimate, making x /= x = True, which kind of ruins 
the equivalence relation thing, no?

Dan

Wolfgang Jeltsch wrote:
> Am Mittwoch, 12. März 2008 00:53 schrieb askyle:
>> […]
> 
>> So if floating point (==) doesn't correspond with numeric equality, it's
>> not FP's fault, but ours for expecting it to do!
> 
> No, I think, it’s the Prelude’s fault to define (==) as “floating point 
> equality”.  We should us a different identifier like floatingPointEq.  (==) 
> is expected to be an equivalence relation.  (I think I already said this.)
> 
>> […]
> 
> Best wishes,
> Wolfgang
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