Re: [Haskell-beginners] error: Not in scope: data constructor `BinTree'

If you don't include "Node a" then there isn't any point in having the a parameter on BinTree as it's never used unless you add another constructor that uses it. I based the modification on the usage in your example where you're trying to store a value of 3. Without that parameter the code becomes: b1 = Node EmptyBinTree EmptyBinTree I haven't tried it, but that will also likely complain it can't deduce "a" from the usage. -R. Kyle Murphy Sent from my phone. On Apr 13, 2012 1:03 PM, "Kak Dod" wrote:

Thanks Tom. this is what i wanted I do not want "Node a" there, I wants only Node and Tom's solution works. Thanks to all .

------------------------------ *From:* Tom Murphy *To:* Kak Dod *Cc:* Kyle Murphy ; "beginners@haskell.org" < beginners@haskell.org> *Sent:* Friday, 13 April 2012 4:53 PM *Subject:* Re: [Haskell-beginners] error: Not in scope: data constructor `BinTree'

"(BinTree a)" needs to be in parentheses to pattern-match properly.

data BinTree a = Node (BinTree a) (BinTree) a | EmptyBinTree deriving Show

On 4/13/12, Kak Dod wrote:

...

Thank you but

if I change the code like this:

data BinTree a = Node BinTree a BinTree a | EmptyBinTree deriving Show

b1 = Node 3 EmptyBinTreeEmptyBinTree

Then I am get this error:

bintree.hs:1:23: `BinTree' is not applied to enough type arguments Expected kind `?', but `BinTree' has kind `k0 -> *' In the type `BinTree' In the definition of data constructor `Node' In the data type declaration for `BinTree' Failed, modules loaded: none.

________________________________ From: Kyle Murphy To: Kak Dod Cc: "beginners@haskell.org" Sent: Friday, 13 April 2012 4:38 PM Subject: Re: [Haskell-beginners] error: Not in scope: data constructor `BinTree'

Your constructor is called Node, not BinTree. data BinTree a = Node a (BinTree a) (BinTree a) | EmptyNode b1 = Node 3 EmptyNode EmptyNode -R. Kyle Murphy Sent from my phone. On Apr 13, 2012 12:24 PM, "Kak Dod" wrote:

if i compile the following code I get "bintree.hs:3:13: Not in scope: data constructor `BinTree'"

...

data BinTree a = Node BinTree a BinTree a | EmptyBinTree deriving Show

b1 = (Node (BinTree 3) EmptyBinTree)

please help

-kak

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