tasks a-s

Task/Ordered-Partitions/Haskell/ordered-partitions-2.hs

@@ -0,0 +1,12 @@
+comb :: Int -> [a] -> [([a],[a])]
+comb 0 xs     = [([],xs)]
+comb _ []     = []
+comb k (x:xs) = [ (x:cs,zs) | (cs,zs) <- comb (k-1) xs ] ++
+                [ (cs,x:zs) | (cs,zs) <- comb  k    xs ]
+
+partitions :: [Int] -> [[[Int]]]
+partitions xs = p [1..sum xs] xs
+    where p _ []      = [[]]
+          p xs (k:ks) = [ cs:rs | (cs,zs) <- comb k xs, rs <- p zs ks ]
+
+main = print $ partitions [2,0,2]