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>

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 ⇔. In MathML it also has a > a couple of aliases which are valid -- ⇔ and > ⇔. > > For some reason that I don't know, the TeX name lost out here, and the > obvious guess -- ↔ -- 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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