USE SCALA

Define a polymorphic Tree data type, where a Tree is either a Node with a left subtree, a value, and a right subtree; or it is a Leaf with just a value.

Also define a companion object for the Tree data type, with the following functions:

A polymorphic function, replace, which takes three arguments a Tree t, a value before, and a value after and returns a variant of t with ALL instances of before replaced with the value after.

USE SCALA

USE SCALA