This should do: combinations :: [[a]] -> [[a]] combinations [] = [[]] combinations [[x]] = [[x]] combinations ([] : xxs) = combinations xxs combinations ((h : tl) : xxs) = [h : r | r <- combinations xxs] ++ if null tl then [] else combinations (tl : xxs) Bernd developer@imaginando.net schrieb:
Hi,
I need a functions which takes as argument a list of lists like this one:
[[1,2],[3],[4]]
and gives me a list of list with all the possible combinations like this one:
[[1,3,4],[2,3,4]]
In this case there are only 2 combinations but if there was more than one element in the other lists the results were much more.
I'm a little stuck in this simple problem.
First i was thinking in cartesian product but then i realized that i may not be what i really need.
Any tip?
Many thx,
Nuno Santos
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