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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