Lazy verbose calculator

calc.rb

class VerboseCalculator < Struct.new(:stack)
  NUMBERS = {
    zero:   0,
    one:    1,
    two:    2,
    three:  3,
    four:   4,
    five:   5,
    six:    6,
    seven:  7,
    eight:  8,
    nine:   9,
  }

  OPERATIONS = {
    plus:       :+,
    minus:      :-,
    by:         :*,
    divide_by:  :/,
  }

  def to_i
    current_value = stack.first
    stack.drop(1).each_slice(2) do |op, n|
      current_value = current_value.send(op, n)
    end
    current_value
  end

  NUMBERS.merge(OPERATIONS).each do |k, v|
    define_method(k) do
      stack << v
      self
    end
  end
end

VerboseCalculator::NUMBERS.each do |k, v|
  define_method(k) { VerboseCalculator.new([v]) }
end

raise unless one.plus.one.to_i == 2
raise unless one.plus.one.plus.two.to_i == 4
raise unless two.minus.one.to_i == 1
raise unless three.by.two.to_i == 6
raise unless four.divide_by.two.to_i == 2

puts 'Works!'