[Haskell-cafe] Smarter do notation
fischer at nii.ac.jp
Mon Sep 5 16:49:39 CEST 2011
On Mon, Sep 5, 2011 at 10:19 PM, Thomas Schilling
<nominolo at googlemail.com>wrote:
> a >>= \p -> f <$> b -- 'free p' and 'free b' disjoint
>> ((\p -> f) <$> a) <*> b
> Will there also be an optimisation for some sort of simple patterns? I.e.,
> where we could rewrite this to:
> liftA2 (\pa pb -> f ...) a b
> I think I remember someone saying that the one-at-a-time application of <*>
> inhibits certain optimisations.
liftA2 is defined via one-at-a-time application and cannot be redefined
because it is no method of Applicative. Do you remember more details?
> I find (a << b) confusing. The intended semantics seem to be "effect a",
> then "effect b", return result of "a".
Sorry, I didn't know that << doesn't exist. I meant an operator with the
meaning of <* .
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