rpn calculator

rpn_calc.rb

class RPNCalculator
  def evaluate(rpn)
    expression = rpn.split
    stack = Array.new
 
    unless expression.count > 1
      return expression[0].to_i
    end
 
    expression.each do |e|
      if e == "+" || e == "-" || e == "*" || e == "/"
        op2 = stack.pop.to_i
        stack.push(stack.pop.to_i.send e, op2).to_s  
      else
        stack << e        
      end
    end
    puts stack.first
  end
end

# calc = RPNCalculator.new

# calc.evaluate('1 2 +')   # => 3
# calc.evaluate('2 5 *')   # => 10
# calc.evaluate('50 20 -') # => 30
# calc.evaluate('10 2 /')  # => 5