Hi all, I just started learning Haskell but am having some trouble getting the insertion into a binary search tree to work and was hoping that somebody could advise me on a possible solution. Thanks. Given the data type definition of the tree to be: Code: data Ord a => BST a = EmptyBST | Node ( BST a ) a ( BST a ) deriving (Show, Eq) And the insertion function to be: Code: insert v EmptyBST = Node EmptyBST v EmptyBST insert v (Node b a c) | v<= a = Node a ( insert v b ) c | otherwise = Node a b ( insert v c ) GHCI keeps telling me that I 'cannot construct an infinite type': ' Occurs check: cannot construct the infinite type: a = BST (BST a) Expected type: BST a -> BST (BST a) -> a Inferred type: BST a -> BST (BST a) -> BST (BST a) In the second argument of `Node', namely `(insert v b)' In the expression: Node a (insert v b) c' Upon adding the following signature: Code: insert :: Ord a => a -> BST a -> BST a I get: Occurs check: cannot construct the infinite type. Sorry, but I'm quite lost. Any thoughts? Thanks. Benjamin -- View this message in context: http://haskell.1045720.n5.nabble.com/Beginner-Another-Binary-Search-Tree-Que... Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.