add without carry

[Marc 'BlackJack' Rintsch]

In <1158308274.680123.100070 at i42g2000cwa.googlegroups.com>, Hugh wrote:

> I would like to perform an addition without carrying of two integers...
> I've got no idea how to do this in python, although I've been using it
> for web/cgi/db work for a few years now.

Your description is a bit vague.  What is `without carrying`?  Do you want
to limit the result to a given bit length with a "wrap around" behavior if
the number gets too large to fit into those bits?  Then this should do the
trick:

  a = (b + c) & (2**bits - 1)

Ciao,
	Marc 'BlackJack' Rintsch