[XeTeX] unicode-math package and \UnicodeMathSymbol command

Ross Moore ross at ics.mq.edu.au
Mon Jun 22 04:48:23 CEST 2009

Hi Joel,

On 22/06/2009, at 12:05 PM, Joel C. Salomon wrote:

> Ross Moore wrote:

>> Indeed I think that it is wrong to have this
>> in  unicode-math-add.tex :
>>    \UnicodeMathSymbol{"0003A}{\colon}{\mathpunct}{}%
>> especially so since  unicode-math.tex  already has this:
>>    \UnicodeMathSymbol{"02236}{\colon}{\mathrel}{ratio}
>> which follows AMS usage, but which differs from the original \TeX .
>> It is most unfortunate that, over the years, there has been
>> a lot of confusion about the use of  \colon  and  : .
>> It's not at all clear how this should be sorted out now.
>> Probably it depends upon what font designers have chosen to do.
> This is an issue Will knows about; see the GitHub bug tracker at
> <http://github.com/wspr/unicode-math/issues/#issue/7>.  It’s the  
> Unicode
> folks, not font designers, that have decided the issue (somewhat):  
> ‘:’
> [U+003A] is called “Colon”, the punctuation mark, while  
> ‘∶’ [U+2236] is
> the “Ratio” relation symbol.

By giving them different names they have done something good!

> BTW, I’m not sure what you mean by AMS usage differing from the  
> original
> TeX; both the “Short Math Guide” and the amsmath package  
> documentation
> say that ‘:’ has relation spacing and ‘\colon’ is for  
> punctuation, /à
> la/ the TeXBook.

I was looking at the line in the STIX table:

  02236  uni2236  EE34  2DR  R  ratio  ISOAMSR  P\colon  Colon  r000  
0x2236 6 3B   ratio

which seems to indicate that  \colon  is meant to be the macro for this
symbol, from the ISO-AMS relations block of characters.

I believe this is the reason why it is wrong in  unicode-math.tex .
The later loading of   unicode-math-add.tex  does nothing to fix it.

> It seems that, somewhat counter-intuitively, ‘:’ [U+003A] ought  
> to be a
> synonym for the mathrel ‘∶’ [U+2236], and ‘\colon’ must be  
> used to
> include the actual [U+003A] mathpunct.

The logic, as I understand it, is that when in a math environment,
the ':' symbol is normally used with relation spacing;
e.g., as a substitute notation for \mid  with a set of elements
subject to a condition.
(In this setting the ':' symbol should not be thought of as a colon,
but as an abbreviation for  'such that'  or somesuch.)

If you want a visual effect more akin to a colon in text punctuation,
then use the macro  \colon .

In other words  \colon  and ':' are *not* meant to be alternative ways
of getting the same result. (i.e., *not* the same LICR, in that jargon).

For function notation, roughly   f: A -> B   (in ASCII only)
what I use in serious publications is something like:

\let\from\colon   % in the preamble

     $ f\from A\to B $

which reads pretty much as you would say it.

> —Joel Salomon



Ross Moore                                       ross at maths.mq.edu.au
Mathematics Department                           office: E7A-419
Macquarie University                             tel: +61 (0)2 9850 8955
Sydney, Australia  2109                          fax: +61 (0)2 9850 8114

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