Hi, Please reply to the list so others can contribute. On 11 March 2012 14:42, bahadýr altan wrote:

I'm sorry if I mislead you, I think I didn't mention my problem clearly there. I'm actually stuck in the position of declaring subtrees, I couldn't find a solution to that.

My function is like

f :: Tree -> Tree

And my tree structure is like

data Tree = Empty | Branch Integer Tree Tree

And When I write this which I learned from you : (c1, c2, d1, d2, e1, e2 :: Tree)

I get error. If you tell me How should I solve that I'd appreciate.

Hence I was suggesting to think about the types of the pattern variables. f (Branch x (Branch y y1 y2) (Branch z z1 z2)) = (x,y,y1,y2,z,z1,z2) This definition will work, and return a 7-tuple given a Tree. Try to load this into ghci and see what the type of f is (:t f). One hint: y and y1 aren't of the same type. Ozgur