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

[Thomas Davie]

On 14 Apr 2010, at 09:12, Jonas Almström Duregård wrote:

>> f,g :: Bool -> Int
>> f x = 6
>> g x = 6
>> 
>> We can in Haskell compute that these two functions are equal, without solving the halting problem.
> 
> what about these?
> f,g :: Bool -> Int
> f x = 6
> g x = x `seq` 6

As pointed out on #haskell by roconnor, we apparently don't care, this is a shame...  We only care that x == y => f x == g y, and x == y can't tell if _|_ == _|_.

It's a shame that we can't use this to tell if two functions are equally lazy (something I would consider part of the semantics of the function).

Bob
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