Or, when lists had a decent eliminator defined in the Prelude (just like maybe
for Maybe and either for Either):
list :: b -> (a -> [a] -> b) -> [a] -> b
list d _ [] = d
list _ f (x:xs) = f x xs
fromList = list []
we could write the alternate function like this:
alt :: [a] -> [a]
alt = list [] $ \a -> (a:)
. list [] (const alt)
--
Sebastiaan
On Jun 6, 2010, at 4:46 PM, R J wrote:
> What's the cleanest definition for a function f :: [a] -> [a] that takes a
> list and returns the same list, with alternate items removed? e.g., f [0, 1,
> 2, 3, 4, 5] = [1,3,5]?
>
>
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