refactoring_for_schuchert.rb

class Thing
  # ...

  def take(v)
    @current_mode.call(v)
    @current_mode = Accumulating
  end
end

class Accumulating
  def self.call(stack, v)
    digits = 10**(Math.log10(v).to_i + 1)
    x = stack.pop()
    x *= digits
    x += v
    stack.push(x)
  end
end

class Replacing
  def self.call(stack, v)
    stack.pop()
    stack.push(v)
  end
end

class Inserting
  def self.call(stack, v)
    top = stack.last
    stack.push(top)
    stack.push(v)
  end
end