class MoreMath::StringNumeral

def initialize(string, number, alphabet)
  @alphabet = NumberifyStringFunction.convert_alphabet(alphabet).freeze
  if string
    @string = string.to_s
    string.each_char.each do |c|
      @alphabet.include?(c) or raise ArgumentError,
        "illegal character #{c.inspect} in #{@string.inspect} for alphabet #{@alphabet.inspect}"
    end
  elsif number
    @number = number.to_i
  end
end