Non-exhaustive patterns in function error

Question

In haskel, I got an error and somehow I couldn't find the right solution. There is the error i get and my code:

My code:

data MyTree = Leaf Float | Tree String MyTree MyTree deriving (Show, Eq, Ord)

asgCodeRec1 [] _ = []
asgCodeRec1 (a:b:c) (y:ys) = [Tree (y) (Leaf a) (Leaf b)] ++ asgCodeRec1 c ys

asgCode2 (a:b:c) (x:xs) = [Tree x a b] ++ (if c/=[] then (asgCode2 c xs) else [])

asgCode c y = asgCode2 (asgCodeRec1 c y) (drop (length c * 2) y)

and my console log:

*Main> asgCode [0.5,0.5,0.5,0.5,0.5,0.5] ["and","and","and","or","or"]
*** Exception: part1.hs:6:1-81: Non-exhaustive patterns in function asgCode2

Any help is useful. Thanks.

Answer 1

(drop (length c * 2) y) returns []. [] of course doesn't match (x:xs) (it requires at least a singleton). Does this help?