[Haskell-beginners] A "show" error

[Adrien Haxaire]

On Sun, Mar 11, 2012 at 07:10:28PM +0000, bahadýr altan wrote:
> Hi, 
> I'm trying to process on a tree with this function :
> 
> f (Branch x (Branch y y1 y2) (Branch z z1 z2)) = (x,y,y1,y2,z,z1,z2)
> 
> 
> and my tree declaration is this : 
> 
> data Tree = Empty | Branch Integer Tree Tree deriving (Show)
> 
> And I'm getting this error : 
> 
> Main> f (Branch 12 (Branch 15 Empty Empty) (Branch 28 Empty Empty))
> ERROR - Cannot find "show" function for:
> *** Expression : f (Branch 12 (Branch 15 Empty Empty) (Branch 28 Empty Empty))
> *** Of type    : (Integer,Integer,Tree,Tree,Integer,Tree,Tree)
> 
> I'll be happy if you help me to get rid of this error..

Hello,

Dit you try to derive it automatically, by adding 'deriving (Show)' after its declaration?

Otherwise you need to define it manually I'm afraid.

-- 
Adrien Haxaire 
www.adrienhaxaire.org | @adrienhaxaire