F = Class((obj: Obj) -> F)

greedy(obj) =
    log obj
    F.new greedy

_ = greedy(1)::base(1)::base(1)

Leaf = Class Int
Leaf|<: Show|.
    __str__ ref self = "Leaf(\{self::base})"
Node = Class { left = Tree; right = Tree }
Node|<: Show|.
    __str__ ref self = "Node{ left = \{self::left}; right = \{self::right} }"
Tree = Class Node or Leaf
Tree|<: Show|.
    __str__ ref self = match self::base:
        (l: Leaf) -> l.__str__()
        (n: Node)-> n.__str__()

print! Node.new { left = Tree.new Leaf.new 1; right = Tree.new Leaf.new 2 }