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RE: Primes and subscripts

From: Robert Miner <robertm@dessci.com>
Date: Mon, 8 Jun 2009 13:53:26 -0700
Message-ID: <D1EFB337111B674B8F1BE155B01C6DD60565481A@franklin.corp.dessci>
To: "Cameron McCormack" <cam@mcc.id.au>, <www-math@w3.org>
Hi.

The proper encoding of all "pseudo-scripts" should be via markup.  Other examples of pseudo-scripts are multiple prime characters, backprimes, the degree symbol, and the asterisk.

I understand Unicode decided to make (some) of these characters correspond with glyphs that are reduced in size and raised off the baseline, so they can be used in plain text, but that model doesn't really work with math.  As you note, in mathematics whenever there is a subscript, these are almost universally typeset as stacked scripts.  To do that, one has to use a <msubsup> construct, and the renderer should be smart enough to special case the pseudo-scripts.

A second argument that always comes up is that with the Unicode model is without the markup, there is no structural connection between the operator (the prime) and it's argument (is it the letter before the prime, the parenthesized expression before the prime, etc.) 

At any rate, the official MathML position is that you should use <msubsup>.  Another post recently pointed out that this is such a common question/problem that it really deserves to be addressed directly in the spec, and I think the consensus is that is right, so we will try to add that in the next draft (which we hope will be the Last Call draft).

--Robert


> -----Original Message-----
> From: www-math-request@w3.org [mailto:www-math-request@w3.org] On
> Behalf Of Cameron McCormack
> Sent: Monday, June 08, 2009 3:17 PM
> To: www-math@w3.org
> Subject: Primes and subscripts
> 
> Hi.
> 
> I’m writing some presentation MathML and I’d like to know exatly how I
> should write something.  I have a variable x_1 which I represent with
> <msub><mi>x</mi><mn>1</mn></msub>.  Now I want to have a variable with
> the same name but with a prime after it.  How should I write that?
> Both
> <msub><mi>x</mi><mn>1</mn></msub><mo>&prime;</mo> and
> <msupsub><mi>x</mi><mn>1</mn><mo>&prime;</mo></msupsub> don’t look that
> nice in the tool I am using.
> 
> Thanks,
> 
> Cameron
> 
> --
> Cameron McCormack ≝ http://mcc.id.au/


Received on Monday, 8 June 2009 20:52:55 GMT

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