Add two numbers without the + or - sign [Bug]

[pupipipu]

The bitwise add 2 integers solution will hit infinite loop for negative integers. The carry will keep increasing if the bit length is not bounded.
Proposed solution:

	def sum_two(self,a,b):
                #max bit length, change to 32 for 32bit
		max_positive = 2 ** 64
		min_negative = -2 ** 64

		while b != 0:
			if b == max_positive:
				return a ^ min_negative
			a,b = a ^ b,(a&b)<<1
		return a