gistfile1.rb

class BaseConverter

  def initialize(digits)
    @decimal_digits = "0123456789"
    @digits = digits.to_s
  end

  def from_decimal(i)
    convert(i.to_s, @decimal_digits, @digits)
  end

  def to_decimal(s)
    convert(s.to_s, @digits, @decimal_digits)
  end

  def convert(number, fromdigits, todigits)
    neg = false
    if  number[0].chr == '-'
      neg = true
      number.slice!(/^./)
    end

    x = 0
    number.to_s.each_char do |digit|
      x = x * fromdigits.length + fromdigits.index(digit)
    end

    return todigits[0].chr if x == 0

    res = ""
    while x > 0
      digit = x % todigits.length
      res = todigits[digit].chr + res
      x = (x / todigits.length).to_i
    end
    res = '-' + res if neg
    return res
  end

end