[Haskell-cafe] bit of help with n-ary please...

[spot135]

Anybody? thanks




spot135 wrote:
> 
> 
> Hi,
> 
> Ok what im trying to do is replace an element in an n-ary and display the
> completed tree.
> 
> So this is what ive got so far.
> 
> data Tree a = Empty |Leaf a|Branch a [Tree a]
> 				deriving (Show)
> 
> 
> replace :: Eq a=>a->a->Tree a -> (Tree a)
> 
> replace x y Empty = Element x
> 
> replace x y (Leaf z)
> 	| x==z = (Leaf y)
> --	| otherwise = 
> 	
> replace x y (Branch z lis)
> 	| x==z = (Branch y lis)
> 	|otherwise = replaceA x y clis
> 
> 	
> replaceA :: Eq a=> a->a->[Tree a]->(Tree a)
> replaceA _ _ [] = Empty -- run out
> replaceA x y (h:r)
> 	|Q suc = suc 
> 	|otherwise = replaceA x y r 
> 	where suc=replace x y h 
> 	
> Q :: a -> Bool
> Q a = True
> Q a = False
> 
> Theres two main problems i am having. One is I'm not sure what should be
> the "otherwise" in the leaf function. Another problem is it doesn't show
> the whole tree just the part after the replacement.
> 
> If you think this is complete bull I'll quite happily start over if
> somebody could give me some insight 
> into what is the best way of tackling this problem is.
> 
> Many thanks in advance
> 
> spot
> 
> 
> 
> 

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