[XeTeX] Re: maths delimiter design

[Will Robertson]

On 25/11/2005, at 9pm, Peter Dyballa wrote:

> Am 25.11.2005 um 04:16 schrieb Will Robertson:
>
>> "x+y+z" in maths mode?
>>
>> Are we going to have to make every letter math-active?
>> Or, now that I just think of it, will font mappings come to our  
>> rescue?
>
> x, y, and z are no math symbols, they are, seldomly, used in a math  
> context, in which some programmes tend to 'emphasise' them  
> artificially. + is some US-ASCII character too. (If you want to  
> have the same emphasised look of your copy you need some extra work  
> to add.)
>
> Ross thought of the Unicode blocks starting at U+2150 or at U+27C0,  
> i.e. Number Forms, Arrows, Mathematical Operators, Miscellaneous  
> Math Symbols-A, Supplemental Arrows-A, Supplemental Arrows-B,  
> Miscellaneous Math Symbols-B, Miscellaneous Math Operators, for  
> example ∅, √, ∫, ≈, ≰, ...

But there are also blocks of mathematical letters in normal (that is,  
italic), bold, etc., style.

See <http://www.unicode.org/charts/PDF/U1D400.pdf> that shows the  
range 1D400--1D7FF.

The problem I am talking about is that I, for one, would not want to  
enter such symbols directly, because you lose out on the separation  
of meaning and presentation (or syntax and semantics, or whatever).

Even more subtle is the requirement to typeset the "plain" italic  
symbols of normal maths like "a+b=c".

Using a font with the font mapping
   A -> MATHEMATICAL ITALIC CAPITAL A
   a -> MATHEMATICAL ITALIC SMALL A
   ...
then switching to a font with
   a -> MATHEMATICAL BOLD ITALIC SMALL A
   ...
to typeset (say) vectors solves the problem nicely.

With nice editor support, on the other hand, I can imagine entering  
maths *symbols* directly, since their meaning is generally fixed.

Will