Hello Ron!
Hi there,
I have written this little function:
f :: (Num a, Enum a) => a -> [[a]] f n = [[a]|a<-fu n] ++ [a:[b]|a<-fu n,b<-fu n] ++ [a:b:[c]|a<-fu n,b<-fu n,c<-fu n] fu n = [1..n]
This is an example of the function in action:
*Mod> f 4 [[1],[2],[3],[4],[1,1],[1,2],[1,3],[1,4],[2,1],[2,2],[2,3],[2,4],[3,1],[3,2],[3, 3],[3,4],[4,1],[4,2],[4,3],[4,4],[1,1,1],[1,1,2],[1,1,3],[1,1,4],[1,2,1],[1,2,2] ,[1,2,3],[1,2,4],[1,3,1],[1,3,2],[1,3,3],[1,3,4],[1,4,1],[1,4,2],[1,4,3],[1,4,4] ,[2,1,1],[2,1,2],[2,1,3],[2,1,4],[2,2,1],[2,2,2],[2,2,3],[2,2,4],[2,3,1],[2,3,2] ,[2,3,3],[2,3,4],[2,4,1],[2,4,2],[2,4,3],[2,4,4],[3,1,1],[3,1,2],[3,1,3],[3,1,4] ,[3,2,1],[3,2,2],[3,2,3],[3,2,4],[3,3,1],[3,3,2],[3,3,3],[3,3,4],[3,4,1],[3,4,2] ,[3,4,3],[3,4,4],[4,1,1],[4,1,2],[4,1,3],[4,1,4],[4,2,1],[4,2,2],[4,2,3],[4,2,4] ,[4,3,1],[4,3,2],[4,3,3],[4,3,4],[4,4,1],[4,4,2],[4,4,3],[4,4,4]] *Mod>
This is ofcourse nice and all, but I need a function that does this same trick, but then doesn't only generate listelements of the maximum hard-coded length of three, but to length m, where m is an extra parameter.
See if this meets your needs: cafe1 _ 0 = ([[]],[]) cafe1 n m = let (p,u) = cafe1 n (m-1) new = [i:j | i <- [1..n], j <- p] in (new,u ++ new) cafe2 n = snd . cafe1 n Usage (for your example): Test> cafe2 4 3 [[1],[2],[3],[4],[1,1],[1,2],[1,3],[1,4],[2,1],[2,2],[2,3],[2,4],[3,1],[3,2],[3,3],[3,4], [4,1],[4,2],[4,3],[4,4],[1,1,1],[1,1,2],[1,1,3],[1,1,4],[1,2,1],[1,2,2],[1,2,3],[1,2,4], [1,3,1],[1,3,2],[1,3,3],[1,3,4],[1,4,1],[1,4,2],[1,4,3],[1,4,4],[2,1,1],[2,1,2],[2,1,3], [2,1,4],[2,2,1],[2,2,2],[2,2,3],[2,2,4],[2,3,1],[2,3,2],[2,3,3],[2,3,4],[2,4,1],[2,4,2], [2,4,3],[2,4,4],[3,1,1],[3,1,2],[3,1,3],[3,1,4],[3,2,1],[3,2,2],[3,2,3],[3,2,4],[3,3,1], [3,3,2],[3,3,3],[3,3,4],[3,4,1],[3,4,2],[3,4,3],[3,4,4],[4,1,1],[4,1,2],[4,1,3],[4,1,4], [4,2,1],[4,2,2],[4,2,3],[4,2,4],[4,3,1],[4,3,2],[4,3,3],[4,3,4],[4,4,1],[4,4,2],[4,4,3], [4,4,4]] :: [[Integer]] I haven't lost much time making the function very well written. It should be possible to define it as an unfold. Best Regards, Bruno