[Haskell-cafe] Optimizing unamb by determining the "state" of a
tom.davie at gmail.com
Mon Apr 20 05:19:14 EDT 2009
On 20 Apr 2009, at 10:57, Peter Verswyvelen wrote:
> On Mon, Apr 20, 2009 at 10:23 AM, Thomas Davie <tom.davie at gmail.com>
> Really? Is it any less referentially transparent than unamb already
> is - i.e. it's referentially transparent, as long as the two values
> really are equal.
> I think it is. Suppose we call the function hnf :: a -> Bool. hnf
> might return a different result for the same argument, since the
> evaluation of the argument might be happening on a different thread,
> so the result of hnf depends on the time when it is evaluated. Or
> am I missing something here?
Sure, so hnf would give us a non-determined result, but I don't think
that makes unamb any less referentially transparent – the same value
is always returned, and always reduced at least to hnf.
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