You need to provide a Show instance for your data type. The easiest way is to add 'deriving Show' at the end of your data type declaration.

The errors you get aren't to do with the function f.

On 11 March 2012 16:01, bahadýr altan <doaltan@yahoo.co.uk> wrote:
These are the ones I get, they are the same but they have different inputs :

Main> f (Branch 12 (Branch 7 (Branch 3 Empty Empty) (Branch 10 Empty Empty)) (Branch 24 Empty Empty))
ERROR - Cannot find "show" function for:
*** Expression : f (Branch 12 (Branch 7 (Branch 3 Empty Empty) (Branch 10 Empty Empty)) (Branch 24 Empty Empty))
*** Of type    : (Integer,Integer,Tree,Tree,Integer,Tree,Tree)


Main> f (Branch 13 (Branch 2 Empty Empty) (Branch 48 Empty Empty))
ERROR - Cannot find "show" function for:
*** Expression : f (Branch 13 (Branch 2 Empty Empty) (Branch 48 Empty Empty))
*** Of type    : (Integer,Integer,Tree,Tree,Integer,Tree,Tree)

To be clear, I need to get a tree as an input. I mean the output should be like this : 

f (Branch a (Branch b (Branch d Empty Empty) (Branch e Empty Empty)) (Branch c Empty Empty)) = Branch b (Branch d Empty Empty) (Branch a (Branch e Empty Empty) (Branch c Empty Empty))


Thank you very much for helping me I really appreciate it :)

From: Ozgur Akgun <ozgurakgun@gmail.com>
To: bahadýr altan <doaltan@yahoo.co.uk>; Haskell Beginners <beginners@haskell.org>
Sent: Sunday, 11 March 2012, 17:50

Subject: Re: [Haskell-beginners] Type Tree variables

What's the error you get?

On 11 March 2012 15:37, bahadýr altan <doaltan@yahoo.co.uk> wrote:
I tried "f" function but it always give errors. Thanks anyway..

Ozgur





--
Ozgur Akgun