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Re: Accents in the operator dictionary

From: Frédéric WANG <fred.wang@free.fr>
Date: Thu, 22 Apr 2010 11:45:33 +0200
Message-ID: <4BD01ABD.7080202@free.fr>
To: neils@dessci.com
CC: Neil Soiffer <neil.soiffer@gmail.com>, "www-math@w3.org" <www-math@w3.org>
For "check mark" I don't see why it would be a mathematical operator, so 
it's fine if it is removed.

1) and 2) are actually related. I was wondering if the rules to 
determine the form are enough to choose the accent in case 2), even when 
there are multiple forms (there was the same problem with "tilde", but 
apparently there are now two distinct operators "tilde" and "tilde 
operator"). My answer to 1) was that these accent operators are used in 
munder/mover/munderover after the operand (the base of 
munder/mover/munderover) so they are postfix. I try to justify it by the 
rules below, but I failed:

http://www.w3.org/TR/MathML3/chapter3.html#presm.formdefval

For low line, I don't see what is this infix operator but I was not 
asking to remove it from the dictionary. Rather than dealing with each 
particular case I would prefer a general solution. For Mozilla, if 
accents are really postfix, I was thinking on adding the rule above when 
the operator is a child of munder/mover/munderover other than the base 
(why do you think about that, Karl?)... However, the spec does not seem 
to allow implementers to define their own heuristic rules.

On 22/04/2010 00:15, Neil Soiffer wrote:
>
>
> 2010/4/21 Frédéric WANG <fred.wang@free.fr <mailto:fred.wang@free.fr>>
>
>     So questions/remarks:
>
>     1) What is the rationale for defining most accents as "postfix"
>     operators?
>
>
> I don't know the rationale, but I can guess... it is probably some 
> holdover from when combining chars were used for accents (even though 
> they are not supposed to be used as combining chars).  I was going to 
> say that some, such as U+02C6 are often interchangeable with their 
> combining char "equivalents" (eg, U+0302 in this case), but U+0302 is 
> not listed as stretchy (which seems wrong).
>
>
>     2) The rules for determining the form and the operator dictionary
>     make this two cases behave differently:
>       - low line: <mover><mi>abcdef</mi><mo>_</mo></mover> (form =
>     infix, so not stretchy)
>       - overline: <mover><mi>abcdef</mi><mo>&#x203E;</mo></mover>
>     (form = postfix, so stretchy)
>
>
> I agree that "low line" seems wrong.
>
>     3) Why is "check mark" a stretchy accent (or even just a
>     mathematical operator)? Is it related to \widecheck (caron) or
>     square root?
>
>
> I'm not sure when we decided to eliminate it, but "check mark" is not 
> in the current draft.  See
> http://monet.nag.co.uk/~dpc/draft-spec/appendixc.html 
> <http://monet.nag.co.uk/%7Edpc/draft-spec/appendixc.html>
>
>
> Note:  the Operator Dictionary is non-normative, so you can ignore it 
> as you please.  Nevertheless, it would be good to remove as many 
> errors as possible from it.  We'll discuss these problems at our next 
> MathML meeting.  If you find more, please send them along.
>
> Neil Soiffer
> Senior Scientist
> Design Science, Inc.
> www.dessci.com <http://www.dessci.com>
> ~ Makers of MathType, MathFlow, MathPlayer, MathDaisy, WebEQ, Equation 
> Editor ~
>
>
>     -- 
>     Frédéric Wang.
>     www.maths-informatique-jeux.com
>     <http://www.maths-informatique-jeux.com>
>     www.maths-informatique-jeux.com/international
>     <http://www.maths-informatique-jeux.com/international>
>
>


-- 
Frédéric Wang.
www.maths-informatique-jeux.com <http://www.maths-informatique-jeux.com>
www.maths-informatique-jeux.com/international 
<http://www.maths-informatique-jeux.com/international>
Received on Thursday, 22 April 2010 09:43:07 GMT

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