Reverse Polish Calculator - Version 1 (much better!)

rp_calc2.rb

# version 2 of 2
# updated to handle negative numbers, removed while loop, and uses send method

class RPNCalculator

  def evaluate(string)
    array = string.split
    output = []

    array.each do |x|
      if not x =~ /-?\d/ #if current item is not a digit
        holder = output.pop(2)
        x = holder[0].send(x, holder[1])
      end
      output << x.to_i
    end

    output.pop
  end
end