[Haskell-cafe] Re: instance Eq (a -> b)

Ashley Yakeley ashley at semantic.org
Wed Apr 14 17:58:25 EDT 2010

On 2010-04-14 13:59, roconnor at theorem.ca wrote:

> There is some notion of value, let's call it proper value, such that
> bottom is not one.
> In other words bottom is not a proper value.
> Define a proper value to be a value x such that x == x.
> So neither undefined nor (0.0/0.0) are proper values
> In fact proper values are not just subsets of values but are also
> quotients.
> thus (-0.0) and 0.0 denote the same proper value even though they are
> represented by different Haskell values.

The trouble is, there are functions that can distinguish -0.0 and 0.0. 
Do we call them bad functions, or are the Eq instances for Float and 
Double broken?

Ashley Yakeley

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