On 9/23/2014 4:16 AM, blindanagram wrote:
What is the rationale for gcd(x, y) in Fractions returning a negative value when y is negtive?
For example gcd(3, -7) returns -1,
Since the doc says "the result will have the same sign as b", this is intentinal. However, I consider this a *design* bug. Both -1 and +1 are common divisors, and 1 is the greatest. So I consider the previous line "Calculate the Greatest Common Divisor of a and b" to be incorrect.
which means that a co-prime test that would work in many other languages 'if gcd(x, y) == 1' will fail in Python for negative y. And, of course, since -|x| is less than |x|, returning -|x| rather than |x| is not returning the greatest common divisor of x and y when y is negative.
-- Terry Jan Reedy -- https://mail.python.org/mailman/listinfo/python-list
