Atoi Implementation in Ruby

Prompt: Implement your own string to number conversion function. Do not use the following: send, eval, to_i, to_f, Integer(str), Float(str), or any similar method to convert your strings to numbers in your RPN evaluator.

You will definitely need “atoi” — converts an ASCII string to an integer. E.g., atoi(“251”) returns the integer 251.

Note: String#bytes is only available in ruby 2.0 and above.

The equivalent to str.bytes is to chain str.each_byte.to_a

Refactored

ASCII_NUM_START = 48
 def ascii_to_i(int_as_str)   #example: "22"
    array_ascii = int_as_str.bytes  # [50,50]
    converted_arr = array_ascii.map {|ascii| ascii - ASCII_NUM_START } # [2,2]
    converted_arr.inject { |sum, n| sum * 10 + n  }  # 22
  end