On Sat, 28 Apr 2007, Hans van Thiel wrote:
Hello All,
The standard function groupBy of List.hs doesn't work as I expect in this case:
groupBy (\x y -> (last x) == (last y)) ["abc", "bd","cac"]
results in:
[["abc"],["bd"],["cac"]]
where I want:
[["abc","cac"], ["bd"]]
I think you must roll your own one. How about repeated 'partition' to extract all elements that have the same trailing character like the head word of the list? I have done this in a more complex setting and called it 'slice': http://darcs.haskell.org/haskore/src/Haskore/Basic/TimeOrderedList.lhs
slice :: (Eq a, Num time) => (body -> a) -> T time body -> [(a, T time body)] slice f perf = let splitByHeadKey pf = fmap (\ev -> let i = f (eventBody ev) (pf0, pf1) = partition ((i==) . f) 0 0 pf in ((i,pf0), pf1)) (listToMaybe pf) in List.unfoldr splitByHeadKey perf