[Python-Dev] Re: PEP 218 (sets); moving set.py to Lib
Eric S. Raymond
Tue, 20 Aug 2002 21:05:17 -0400
Greg Ewing <email@example.com>:
> > Um, the notation is '|' and '&', not 'or' and 'and', and those are
> > what I learned in school.
> Really? The notation I learned in school was big-rounded-U
> for union and big-upside-down-rounded-U for intersection.
> Not available in the ASCII character set, unfortunately.
For historical reasons, there are three different notations for Boolean
algebra in common use. You're describing the one derived from set theory.
I personally favor the one derived from lattice algebra; the distinctive
feature of that one is the pointy and &/| operators that look like /\ and
\/. The third uses | and &.
The set-theoretic notation is the oldest. I think Birkhoff & MacLane
invented the lattice-theory notation in the 1940s. It is probably
*slightly* more popular than the set-theoretic notation. The | & one
is distinctly less common than either, at least among mathematicians;
I think EEs and suchlike may use it more than we do.
> But I agree that | and & are fairlly intuitive substitutes
> for these, and they agree with what you use for bit twiddling.
Not an insignificant point.
<a href="http://www.tuxedo.org/~esr/">Eric S. Raymond</a>