Re: [Haskell-cafe] Thinking about an unlistN

Philip, Thanks. It's not quite that, though. It's more like an adapter for a function with a specific arity. If I have, say, a function f :: a -> a -> a -> a -> b it would be nice to be able to just: unlistN 4 f [1..4] Michael (does look like there's no way to make that fly with the type system however) Philip Neustrom wrote:

I'm no expert, but it looks like the generalization of that would be some f that took a list:

f :: [a] -> b

so what you'd have is a fold, right?

foldr1 :: (a -> a -> a) -> [a] -> a

Best, Philip Neustrom

On Sun, Aug 10, 2008 at 11:47 AM, Michael Feathers wrote:

...

I wrote this function the other day, and I was wondering if I'm missing something.. whether there is already a function or idiom around to do this.

unlist3 :: (a -> a -> a -> b) -> [a] -> b unlist3 f (x:y:z:xs) = f x y z

I was also wondering whether the function can be generalized to N or whether this is just one of those edges in the type system that you can't abstract over.

Thanks,

Michael

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