Re: [Haskell-cafe] Combinations

On Tue, 6 Jun 2006 developer@imaginando.net wrote:

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.

Using the List instance of monads you can simplify things. foldr (Monad.liftM2 (:)) [[]] [[1,2],[3],[4]]

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.

cartesian product can be computed by liftM2 (,)