groupWhen.hs

-- Haskell version of groupWhen 
-- http://fssnip.net/6A
-- 
-- Seq.groupWhen isOdd [3;3;2;4;1;2] = seq [[3]; [3; 2; 4]; [1; 2]]

testList = [3, 3, 2, 4, 1, 2]

groupWhen f [] = []
groupWhen f (x:xs) = ( (x : takeWhile notf xs)  : groupWhen f (dropWhile notf xs))
                    where notf x = not (f x)

isOdd x = mod x 2 == 1

main = print (groupWhen isOdd testList)

-- takeWhile/dropWhile are part of the language (possible in the standard library?) but
-- are pretty easy to create:
getStuff f [] = []
getStuff f (x:xs)
    | f x = (x : getStuff f xs)
    | otherwise = []