Parsing list of list haskell -

hello have function given list returns subset of permutations of it. want make function given list of list produces list of lists using first function. more clear:

delete x [] = [] delete x (y:xs) = if (x==y) (delete x xs)                         else (y:delete x xs)  insert x n [] = [] insert x n xs = take (length xs - n) xs ++ [x] ++ drop (length xs - n) xs  insert_and_delete  x n xs= [insert x n (delete x xs)]  my_permutation x 0 list = insert_and_delete x 0 list my_permutation x n list = insert_and_delete x n list   ++  my_permutation x (n-1) list      --n lenght of list 

my_permuation 5 4 [5,1,1,1] [[5,1,1,1],[5,1,1,1],[1,5,1,1],[1,1,5,1],[1,1,1,5]] my_permutation 3 3 [3,1,1] [[3,1,1],[1,3,1],[1,1,3]] 

now want make function given list of lists eg [[5,1,1,1] , [3,1,1]] return list containing results above :

[[5,1,1,1],[5,1,1,1],[1,5,1,1],[1,1,5,1],[1,1,1,5],[3,1,1],[1,3,1],[1,1,3]] 

my try far:

generate_permutations2 [xs:list] = my_permutation  xs (length(xs:list)) (xs:list) ++ generate_permutations2 [list] 

but when try call get:

generate_permutations2[ [2,1,1], [3,1]] exception: non-exhaustive patterns in function generate_permutations2 

edit if change aguments , add base case:

generate_permutations2 [[]] = [[]] generate_permutations2 (xs:list) = my_permutation  xs (length(xs:list)) (xs:list) ++ generate_permutations2 [list] 

occurs check: cannot construct infinite type: t0 = [t0] expected type: [t0] actual type: [[t0]] in expression: list in first argument of generate_permutations2', namely[list]' in second argument of (++)', namelygenerate_permutations2 [list]'

the compiler complaining generate_permutations2 doesn’t handle case input empty list. add clause generate_permutations2 [] did insert , delete.

editorial:

your intentions lot clearer if added type annotations functions. ghc lot better @ getting root of problem when tell top-level types. plus, other haskell programmers used inferring you’re doing type signatures.