Binary Add

gistfile1.rb

class BinaryPlus
  def initialize(first, second)
    @first, @second = first, second
    # to_s accepts a base to convert to. In this case, base 2.
    @first_bin  = @first.to_s(2)
    @second_bin = @second.to_s(2)
    normalize
  end

  def +
    carry = '0'
    result_bin = ''

    @max_size.times do |i|
      # We want to work in reverse, from the rightmost bit
      index = @max_size - i - 1
      first_bit, second_bit = @first_bin[index], @second_bin[index]

      if first_bit == '1' and second_bit == '1'
        result_bin << carry
        carry = '1'
      else
        if first_bit == '1' or second_bit == '1'
          if carry == '1'
            result_bin << '0'
            # carry remains 1
          else
            result_bin << '1'
            carry = '0'
          end
        else
          result_bin << carry
          carry = '0'
        end
      end
    end

    # Is there still a carry hangin' around?
    result_bin << '1' if carry == '1'

    result_bin.reverse.to_i(2)
  end

  private

  def normalize
    # We want both binary numbers to have the same length
    @max_size   = @first_bin.size < @second_bin.size ? @second_bin.size : @first_bin.size
    @first_bin  = @first_bin.rjust(@max_size, '0')
    @second_bin = @second_bin.rjust(@max_size, '0')
  end
end