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Re: empty set symbol in MathML

From: Andreas Strotmann <Strotmann@rrz.uni-koeln.de>
Date: Mon, 05 Apr 2004 17:17:40 +0200
Message-ID: <40717894.5060505@rrz.uni-koeln.de>
To: www-math@w3.org
Cc: Robert Miner <RobertM@dessci.com>

Hi,

how about using combining characters then -- for example:

 empty set =  &x0030;&x0338;   (digit zero + combining long solidus overlay)
 varnothing  =   &x25cb;&x0338; (white circle + combining long solidus 
overlay)

I think it would be perfectly reasonable for MathML to define that an 
entity expands into a sequence of Unicode characters, not a single one.  
Combining characters are meant for this purpose, aren't they?

 -- Andreas

Robert Miner wrote:

>Hi.
>
>Other experts will correctly me if I'm wrong, but my memory is that
>Unicode doesn't acknowledge these as separate character. Instead, they
>are regarded a "glyph variants" of the same character, and thus they
>do not get separate code points.
>
>This is supported by a quick search of the Unicode 4 character
>database.  Another family of characters that are separate in TeX, and
>for which we requested separate codepoints are the long arrows.  In
>this case also, Unicode rules they were glyph variants.
>
>Consequently, apart from the inherently fragile <mglyph> construct,
>there is no good way to distiguish these characters within MathML.
>
>--Robert
>
>
>  
>
>>In the MathML 2.0 spec the entities: &empty; and &emptyv; are mapped 
>>to the same unicode number 2205, but these are different symbols in LaTeX.
>>
>>empty,                     U02205, /emptyset - zero, slash, [EMPTY SET]
>>emptyv,                    U02205, /varnothing - circle, slash, [EMPTY SET]
>>
>>
>>Rendering in LaTEX:
>>  /emptyset  =  zero, slash,
>>  /varnothing  = circle, slash
>>
>>
>>MathPlayer 2.0 renders U02205 (empty and emptyv) as slahed circle, while Mozilla renders U02205  as slahed zero.
>>
>>
>>
>>
>>Is the entity &empty; mapped to the wrong unicode? 
>>    
>>
>
>
>
>------------------------------------------------------------------
>Dr. Robert Miner                                RobertM@dessci.com
>MathML 2.0 Specification Co-editor                    651-223-2883
>Design Science, Inc.   "How Science Communicates"   www.dessci.com
>------------------------------------------------------------------
>
>
>  
>
Received on Monday, 5 April 2004 11:18:00 GMT

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