New submission from Brian Gladman: There is a discussion of this issue on comp.lang.python
The function known as 'the greatest common divisor' has a number of well defined mathematical properties for both positive and negative integers (see, for example, Elementary Number Theory by Kenneth Rosen). In particular gcd(a, b) = gcd(|a|, |b|). But the Python version of this function in the fractions module doesn't conform to these properties since it returns a negative value when its second parameter is negative. This behaviour is documented but I think it is undesirable to provide a function that has the well known and widely understood name 'gcd', but one that doesn't match the behaviour normally associated with this function. I hence believe that consideration should be given to changing the behaviour of the Python greatest common divisor function to match the mathematical properties expected of this function. If necessary a local function in the fractions module could maintain the current behaviour. ---------- components: Library (Lib) messages: 227410 nosy: b...@gladman.plus.com priority: normal severity: normal status: open title: GCD in Fractions type: behavior versions: Python 3.4 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue22477> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
