Reverse Polish Notation Ruby Test with Standard In / Out, Error Handling and History

test.rb

#!/usr/bin/env ruby

class Controller
  def initialize debug = false
    puts 'Enter your Reverse Polish Notation (Example: 5 ! 1 2 + 4 * + 3 -), 
          Enter q to Quit,
          Enter t to Test,
          Enter d to Debug'
    while true
      input = $stdin.gets.strip
      if input == 'q' then exit
      elsif input == 't' then Test.new
      elsif input == 'd' then debug = true; puts "Entering Debug Mode"
      else 
        begin
          puts "Answer: #{Calculator.new(input).answer}"
        rescue Exception => e  
          puts "You did not use reverse polish notation"
          puts e.message if debug
          puts e.backtrace.inspect if debug  
        end 
      end 
    end
  end
end

class Sum_All
  def initialize math
    answer = math.split(' ').inject([]) do |problem, item|
      if item.match(/\d+/) then problem = problem.to_f + item.to_f end
    end
  end
end

class Calculator
  def initialize math
    @answer = math.split(' ').inject([]) do |problem, item|  
      @problem = problem 
      if item.match(/\d+/) then @problem << item.to_f
      else
        sample = @problem.pop(2)
        case 
          when item == '!' then @problem << self.factorial(sample[0])  
          when item == '^' then self.** sample
          when item == '+' then self.+ sample
          when item == '-' then self.- sample 
          when item == '*' then self.* sample 
          when item == '/' then self./ sample
        end
      end
    end
  end

  def factorial f
    return 1 if f == 0
    f * factorial(f-1)
  end

  def method_missing m, *args
    @problem << eval("#{args[0][0]} #{m} #{args[0][1]}")
  end

  def answer
    return @answer.pop
  end
end

class Test
  def initialize
    puts "Running through test sequence"
    self.addition "5 2 +"
    self.subtraction "5 2 -"
    self.multiplication "5 2 *"
    self.division "5 2 /"
    self.factorial "5 !"
    self.exponents "5 2 ^"
    self.original "5 1 2 + 4 * + 3 -"
    self.final "5 ! 1 2 + 4 * + 3 - 2 ^"
  end

  def method_missing m, *args
    answer = Calculator.new(*args).answer
    puts "Testing #{m} #{args} = #{answer}"
  end
end
 
c = Controller.new