Question

I have this tree node :

type Tree<'T when 'T: comparison> = 
| Empty 
| Node of 'T * Tree<'T> * Tree<'T>

but I cant find out a good insert function.

I don’t want to do a interactive program, the input should be a list that is inserted to the tree.

Answer 1

If you don’t need the tree to be balanced then you can use:

let rec insert value = function
| Empty -> Node(value, Empty, Empty)
| Node(v, left, right) when value < v -> Node(v, insert value left, right)
| Node(v, left, right) when value > v -> Node(v, left, insert value right)
| Node(_, _, _) as n -> n

You can insert a list of values into a tree with:

let insertAll list tree = List.fold (fun t e -> insert e t) tree list