public static NaturalNumber ReadFromString(String s, int radix)
	{
		NaturalNumber n;
		int i;
		char a[];
		
		n = new NaturalNumber(0);
		if(n == null)
		{
			return null;
		}
		
		a = s.toCharArray();
		
		for(i = 0;
		    i < a.length && (NaturalNumber.IsDigit(a[i], radix) ||
		                     a[i] == ',');
		    i++)
		{
			if(a[i] != ',')
			{
				if(!n.MultiplyByOneDigit(radix))
				{
					return null;
				}
				if(!n.AddOneDigit(NaturalNumber.CharToDigit(a[i])))
				{
					return null;
				}
			}
		}
		
		return n;
	}