[Python-Dev] Re: PEP 218 (sets); moving set.py to Lib

Greg Ewing greg@cosc.canterbury.ac.nz
Thu, 22 Aug 2002 11:25:07 +1200 (NZST)

"Eric S. Raymond" <esr@thyrsus.com>
Subject: Re: [Python-Dev] Re: PEP 218 (sets):

> Is it + for disjunction and juxtaposition for conjunction, or the other
> way around?

+ is 'or' and juxtaposition (or sometimes a dot) is 'and'
(I prefer those words because they're shorter than
'disjunction' and 'conjunction', and I can remember which
is which:-).

These are probably where Wirth got the idea of using
+ and * from in Pascal -- 'or' is considered the
'addition' operator in boolean algebra, and 'and'
the 'multiplication' operator. (Although the two are
actually completely symmetrical in their algebraic
properties, so it's an arbitrary choice.)

Greg Ewing, Computer Science Dept, +--------------------------------------+
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