On 8/9/07, Chad Scherrer <[EMAIL PROTECTED]> wrote: > > extract :: [Int] -> [a] -> [a] > extract = f 0 > where > f _ _ [] = [] > f _ [] _ = [] > f k nss@(n:ns) (x:xs) = if n == k then x:f (k+1) ns xs > else f (k+1) nss xs
Finally, even if no one else is using it, it would be good to settle > on reasonable names for things more easily. Is there a better name for > this function? Is there a reason not to call it "extract"? Other possible names which occur to me include select, slice, mask. I think I like 'select' best myself, but 'extract' works too. Amusingly, extract is intimately related to function composition. Suppose we have listify :: (Int -> Int) -> [Int] listify = flip map [0..] Then if f, g :: Int -> Int, and f is monotonically increasing, we have the identity (listify f) `extract` (listify g) = listify (g . f) This randomly occurred to me as I was falling asleep last night and I thought I would share. =) -Brent
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
