A Ruby implementation of a binary tree and its catamorphism

tree.rb

class Tree
  attr_reader :value, :left, :right

  def initialize(value, left, right)
    @value = value
    @left = left
    @right = right
  end

  def reduce(initial, &block)
    left_acc = left.reduce(initial, &block)
    right_acc = right.reduce(initial, &block)

    block.call(value, left_acc, right_acc)
  end

  def inspect
    reduce("leaf") { |val, l, r| "#{val} (#{l}, #{r})" }
  end
end

class Leaf
  def reduce(initial, &block)
    initial
  end
end


# This section makes it easy to load up a tree in a console and experiment on it
# Run the script with `ruby tree.rb`

tree = Tree.new(
  5,
  Tree.new(4, Leaf.new, Leaf.new),
  Tree.new(
    3,
    Tree.new(2, Leaf.new, Leaf.new),
    Leaf.new
  )
)

binding.irb