reverse associativity

class Leaf
    getter name

    def initialize(@name : String)
    end

    def to_s(io)
        io << "#{@name}"
    end
end

class Op
    getter left
    getter right

    def initialize(@left : Node, @right : Node)
    end

    def to_s(io)
        io << "(#{@left} -> #{@right})"
    end
end

alias Node = Op | Leaf

def to_array(a : Array(Node), node : Node)
    case node
    when Leaf
        a.push node
    when Op
        to_array a, node.left
        to_array a, node.right
    end
end

def reverse_associativity(tree : Node)
    a = [] of Node
    to_array(a, tree)

    return a.reverse.reduce { |acc, i| Op.new(i, acc) }
end

a = Leaf.new "a"
b = Leaf.new "b"
c = Leaf.new "c"
d = Leaf.new "d"
e = Leaf.new "e"
f = Leaf.new "f"

tree = Op.new(Op.new(Op.new(Op.new(Op.new(a, b), c), d), e), f)

puts tree
puts reverse_associativity tree