How's this?
What about ++, in Haskell thats just an ordinary function, yet you are using the library one in this case. The other thing is that the first definition of my_concat_map is entirely redundant, the second one handles both cases anyway. Also, for completeness, you might be interested to find that in some compilers the list is actually defined as: data [] a = [] | (:) a ([] a) This isn't legal Haskell 98, but nhc and Yhc both define a list similarly to this. Thanks Neil
myhead :: [a] -> a myhead (x:xs) = x
mytail :: [a] -> [a] mytail (x:xs) = xs
mymap :: (a -> b) -> [a] -> [b] mymap fn [] = [] mymap fn (x:xs) = fn x : mymap fn xs
myconcat :: [[a]] -> [a] myconcat (x:xs) = x ++ myconcat xs myconcat [] = []
-- For each a in [a], produce a [b] in another list, then concat the -- list. my_concat_map :: (a -> [b]) -> [a] -> [b] my_concat_map fn [] = [] my_concat_map fn xs = myconcat (mymap fn xs)
stateslist :: StateNode a -> [a] stateslist(State x) = [x] stateslist (CompositeState xs) = my_concat_map stateslist xs _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe