12 Nov
2015
12 Nov
'15
1:22 p.m.
How about: computeHead f = take 1 . fmap f Martin Dennis Raddle:
What would be an elegant way of writing this
computeHead :: (a -> [b]) -> [a] -> [b]
Where when [a] is null, it returns a null list, but when [a] contains one or more elements, it applies the given function to the head of a and returns that? Is there some existing typeclass operator that facilitates this?
You can write
computeHead _ [] = [] computeHead f (x:_) = f x
But that first line seems suspicious to me... it makes me think about how in the list Monad, an empty list falls through. But I can't quite make it work.
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