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Re: content for characters

From: Tim Bagot <tsb-w3-math-0001@earth.li>
Date: Thu, 21 Jun 2001 16:15:11 +0000 (UTC)
To: <www-math@w3.org>
Message-ID: <Pine.LNX.4.33.0106211606350.1183-100000@windle.hack>
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

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