On Jan 31, 4:10*am, Scott David Daniels <(E-Mail Removed)> wrote:

> Grant Edwards wrote:

> > On 2009-01-30, MRAB <(E-Mail Removed)> 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