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 _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe