- From: Tim Bagot <tsb-w3-math-0001@earth.li>
- Date: Thu, 21 Jun 2001 16:15:11 +0000 (UTC)
- To: <www-math@w3.org>
At 2001-06-21T09:59-0400, Andreas Strotmann wrote:-
> In OpenMath, it could be defined using a construct that I believe I
> proposed some years ago for this general purpose, namely, the "one_of"
> operator, which takes a set or list as an argument, and produces an
> arbitrary element of the set or list. Using this, the semantics of +/-
> can be expressed as
>
> for all x, +/-( x ) := one_of ({+x, -x}) .
> The "one_of" construct fits nicely into the basic set of set-theoretic
> operators, as it closely corresponds to the use of the axiom of choice.
Interesting. I hadn't thought about it that way before. As an alternative,
why not a map function to find the image of a set or list under a given
function? This provides another way to avoid having to redefine operators,
and would probably be useful elsewhere. Reuse of choices is a little
harder this way, but not impossible.
Tim Bagot
Received on Thursday, 21 June 2001 12:15:17 UTC