module BCD

# File lib/bcd.rb, line 9
def self.decode(bcd)
  raise ArgumentError, 'Argument is not numeric' unless bcd.is_a? Numeric
  raise ArgumentError, 'Cannot be a negative integer' if bcd < 0

  binstring = ''
  while true do
    q, r = bcd.divmod(10)
    nibble = r.to_s(2)
    while nibble.length < 4 do
      nibble.prepend('0')
    end
    binstring.prepend(nibble)
    q == 0 ? break : bcd = q
  end

  binstring.to_i(2)
end

# File lib/bcd.rb, line 28
def self.encode(int)
  raise ArgumentError, 'Argument is not numeric' unless int.is_a? Numeric
  raise ArgumentError, 'Cannot be a negative integer' if int < 0

  bcdstring = ''
  while int > 0 do
    nibble = int % 16
    bcdstring.prepend(nibble.to_s)
    int >>= 4
  end
  bcdstring.to_i
end