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RE: LeftRightArrow equivalence operator?

From: Hugh J. Devlin <devlinh@nwu.edu>
Date: Sat, 9 Oct 1999 17:34:29 -0500
To: "Robert Miner" <rminer@geomtech.com>
Cc: <www-math@w3.org>
Message-ID: <000001bf12a6$732774e0$3fba6981@devlin>
Mr. Miner,

Thanks for your reply and for your work on MathML.
Sorry if my question was not clear.
I found the Unicode character and the MathML alias I was looking for,
but I guess I was asking more about MathML,
where's the content mark-up element for "equivalence", "biconditional"?
As I understand it, as a MathML user I can't add a content mark-up element
without editing the mathml.dtd.
Maybe I don't have a question as much as a suggestion for an addition to the
content mark-up elements in some future rev.

Thanks again,
Hugh
Hugh J. Devlin
devlinh@nwu.edu


> -----Original Message-----
> From: Robert Miner [mailto:rminer@geomtech.com]
> Sent: Saturday, October 09, 1999 12:46 PM
> To: devlinh@nwu.edu
> Cc: www-math@w3.org
> Subject: Re: LeftRightArrow equivalence operator?
>
>
>
> Hi Hugh,
>
> > The MathML rec includes a RightArrow, implies content element, but
> > apparently absent is a LeftRightArrow, equivalence operator. Unless I'm
> > missing something?
>
> I think you're missing something.  I assume you are using TeX
> terminology here, and are thinking of a double arrow with heads at
> both ends typically indicating the (logicial) equivalence "if and only
> if".
>
> The official unicode point for that character is 0x21D4 and its
> official unicode entity name is &hArr;.  In MathML it also has a
> a couple of aliases which are valid -- &Leftrightarrow; and
> &DoubleLeftRightArrow;.
>
> For some reason that I don't know, the TeX name lost out here, and the
> obvious guess -- &LeftRightArrow; -- is actually a synonym for TeX's
> \leftrightarrow.
>
> In general, most of these naming issues came up as uncomfortable
> compromises.  MathML has *lots* more characters (and specifically
> arrows) than TeX and though in general we tried very hard to stay
> compatible with TeX names, that wasn't always possible, especially
> since TeX, LaTeX, AMSTeX etc are not always consistent amongst
> themselves.
>
> --Robert
>
> ----------------------------------------------------------------
> Robert Miner                          http://www.webeq.com
> Geometry Technologies, Inc.           email: rminer@geomtech.com
>                                       phone: 651-223-2884
> ----------------------------------------------------------------
>
>
Received on Saturday, 9 October 1999 18:38:07 GMT

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