Reverse Polish Notation Calculator

RPNCalc.rb

class RPNCalculator

  def cleaner(idx)
    @data_array.delete_at(idx)
    @data_array.delete_at(idx-1)
  end

  def add(val,idx)
    @data_array[idx-2] = (@data_array[idx-2].to_i).+((@data_array[idx-1].to_i))
    cleaner(idx)
  end

  def sub(val,idx)
    @data_array[idx-2] = (@data_array[idx-2].to_i).-((@data_array[idx-1].to_i))
    cleaner(idx)
  end

  def mul(val,idx)
    @data_array[idx-2] = (@data_array[idx-2].to_i).*((@data_array[idx-1].to_i))
    cleaner(idx)
  end

  def evaluate(data)
    @data_array = data.split
      while @data_array.length > 1
        @data_array.each_with_index do |val,idx|
          if @data_array[idx] == '+'
            add(val,idx)
          elsif @data_array[idx] == '*'
            mul(val,idx)
          elsif @data_array[idx] == '-'
            sub(val,idx)
          end
        end
      end
    return @data_array.first
  end
end

# uncomment below to try out the RPN Calc:

#calc = RPNCalculator.new

#calc.evaluate('6 2 *')
#calc.evaluate('20 10 5 4 + * -')
#calc.evaluate('1 2 + 3 4 + *')
#calc.evaluate('1 2 3 4 + + +')

RPNCalc_1.rb

# NB: This one is not fully functional, but I wanted to leave it here anyways.
# I guess for the audiences viewing pleasure :)

class RPNCalculator
  def initialize
    @op = ['+','-','*']
  end
  
  def cleaner(index)
    @ca.delete_at(index) 
    @ca.delete_at(index-1)
  end
  
  def add(value,index)
    @ca[index-2] = (@ca[index-2].to_i).+((@ca[index-1].to_i)).to_s
    cleaner(index)
  end
  
  def sub(value,index)
    @ca[index-2] = (@ca[index-2].to_i).-((@ca[index-1].to_i)).to_s
    cleaner(index)
  end
  
  def mul(value,index)
    @ca[index-2] = (@ca[index-2].to_i).*((@ca[index-1].to_i)).to_s
    cleaner(index)   
  end
  
  
  def evaluate(n)
    @ca = n.split
      while @ca.length > 1
        @ca.each_with_index do |value,index|
          if @op.include?(value) 
            add(value,index) if @ca[index] == '+'
            sub(value,index) if @ca[index] == '-'
            mul(value,index) if @ca[index] == '*'
          end
        end
      end
    return @ca.first
  end
end


# uncomment below to try out the RPN Calc:

#calc = RPNCalculator.new

#calc.evaluate('6 2 *')
#calc.evaluate('20 10 5 4 + * -')
#calc.evaluate('1 2 + 3 4 + *')
#calc.evaluate('1 2 3 4 + + +')

RPNCalc_2.rb

# even shorter, thanks to a method called 'eval' 
# it evaluates a ruby expression within a string - just what I needed :)
# let's me get rid of the three different calculation functions and the if / elsif statements!


class RPNCalculator

  def cleaner(idx)
    @data_array.delete_at(idx)
    @data_array.delete_at(idx-1)
  end

  def do_math(val,idx)
    @data_array[idx-2] = eval("#{@data_array[idx-2]} #{val} #{@data_array[idx-1]}")
    cleaner(idx)
  end

  def evaluate(data)
    @data_array = data.split
      while @data_array.length > 1
        @data_array.each_with_index do |val,idx|
          if ['+','*','-'].include? val
            do_math(val,idx)
          end
        end
      end
    return @data_array[0].to_i
  end
end


# uncomment below to try out the RPN Calc:

#calc = RPNCalculator.new

#calc.evaluate('6 2 *')
#calc.evaluate('20 10 5 4 + * -')
#calc.evaluate('1 2 + 3 4 + *')
#calc.evaluate('1 2 3 4 + + +')

So...my first attempt wasn't working in all cases...

Added a second which should do the trick.
Cleaner code, changed some variable names and got rid of the initialize method (not needed).

And another version with even more refactoring!
This time supersexy via eval method :)
I guess I should read through ALL of the core ruby documentation