On Jan 31, 4:10 am, Scott David Daniels <scott.dani...@acm.org> wrote: > Grant Edwards wrote: > > On 2009-01-30, MRAB <goo...@mrabarnett.plus.com> wrote: > >> Eric Kang wrote: > >>> In two's complement representation, can adding one positive > >>> and one negative give you overflow? > >> No. > > AFAIK, in Python adding integers never gives you overlow > > regardless of sign. > > Right, but he wants his homework answer.
For extra brownie points, here's a simple proof of the more general proposition that adding a non-negative integer p and a non-positive integer n can't overflow whatever the representation. Let a be the most negative integer and b the most positive. So we're given a <= n <= 0 <= p <= b and need to show that a <= (p + n) <= b. max(p) is b, max(n) is 0, so max(p + n) is b. Similarly min(p + n) is a. Q.E.D. IEEE 754 floating point? I don't know. Go read the standard :-) -- http://mail.python.org/mailman/listinfo/python-list