Brainf**k interpreter in Ruby

Question

I wrote this interpreter for a code challenge. Can this be written any cleaner/smaller? Could I reduce the amount of nested conditional/loops?

def brain_luck(code, input)
  output = ''
  cp = 0 # code pointer
  dp = 0 # data pointer
  ip = 0 # input pointer
  data = Array.new(10, 0)
  while cp < code.length
    case code[cp]
    when '>'
      dp += 1
      if dp == data.length
        data.push(0)
      end
    when '<'
      dp -= 1
      if dp == -1
        dp = 0
        data.unshift(0)
      end
    when '+'
      data[dp] = (data[dp].ord+1)%256
    when '-'
      data[dp] = (data[dp].ord-1)%256
    when '.'
      output += data[dp].chr
    when ','
      data[dp] = input[ip].ord
      ip += 1
    when '['
      if data[dp] == 0
        nest_count = 1
        while nest_count > 0
          case code[cp += 1]
          when '[' then nest_count += 1
          when ']' then nest_count -= 1
          end
        end
      end
    when ']' 
      if data[dp] != 0
        nest_count = 1
        while nest_count > 0
          case code[cp -= 1]
          when ']' then nest_count += 1
          when '[' then nest_count -= 1
          end
        end
      end
    end
    cp += 1
  end
  output
end

Answer 1

Sure it can!

Steps I see to make it clean:

1. Create a class, define state attrs:

   private
   
   attr_reader :output, :code_pointer, :data_pointer, :input_pointer
   

2. define initialize method

   def initialize(args = {})
     @code = args[:code]
     @input = args[:input]
     @output = ''
     @code_pointer, @data_pointer, @input_pointer = 0, 0, 0
   end
   

3. define whens as a methods and give it right names: next_cell, prev_cell, increment, decrement, write_byte, read_byte and so on

4. define constant for configuration:

   OPERATORS = {
     '>' => :next_cell,
     '<' => :prev_cell,
     '+' => :increment,
     ...
   }
   

5. define method to evaluate code:

   def evaluate_code
     code.each { |operator| public_send OPERATORS[operator] }
   end
   

6. Finally instantiate object of your class and call evaluate_code

   BrainLuck.new(code: code, input: input).evaluate_code
   

I think you'll love your object oriented result.