Adding swap/compose functions to Data.Tuple and Data.Function
johnw at fpcomplete.com
Tue Nov 20 20:28:15 CET 2012
>>>>> Edward Kmett <ekmett at gmail.com> writes:
> Data.Tuple already contains swap.
Yeah, and I'm finding it just fine with Hoogle now. I'm not sure how I was
led into thinking it didn't exist, but I had reached for it one day and my
hands came up empty.
> compose :: [(a -> a)] -> a -> a
> compose = foldr (.) id
> composeM :: [(a -> m a)] -> a -> m a
> composeM = foldr (<=<) return
> The composition of them is obvious, and the suggested names already exist
> commonly in a lot of third party code for all sorts of purposes.
> The pain of adoption plus the annoyance of trying to find them exceeds, to
> me, the utility of adding them.
Fair enough. It does seem that the idiom deserves a name, though, considering
how often I've come across it, but perhaps that ship has sailed.
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