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Mailing list for the LaTeX3 project <[log in to unmask]>
Hans Aberg <[log in to unmask]>
Tue, 22 May 2001 12:04:36 +0200
Mailing list for the LaTeX3 project <[log in to unmask]>
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At 23:20 +0200 2001/05/21, Lars Hellström wrote:
>>Could you define the _problem_ you are trying to solve?
>...On one side, the problem is that in LaTeX today, I'm not
>expected to write what I mean in math, I'm expected to specify the visual
>expression for what I mean. This goes very much against the general trend
>in the development of LaTeX, which is that you should say what you mean and
>leave to the style (documentclass, packages used, preamble declarations,
>etc.) to sort out what is the visual expression for this.

There is nothing wrong with this objective in itself, but the complication
is the diverse use of mathematics and how mathematicians write it.

>Now what would a math font designer who cuts only one glyph variant of
>epsilon do today? Most likely put that epsilon in both slot "0F and slot
>"22 of the OML-encoded font in the family. This will work fine until that
>day when comes a document where (in the spirit of Hans Aberg but against
>better judgement)

The problem here is that what one mathematian consider is poor judgement
may be what another finds is better judgement.

> \epsilon and \varepsilon are used to mean different
>things---then the typeset result will be wrong but LaTeX doesn't know this
>and thus cannot give a warning about it.

I don't think this will ever happen, as Unicode now has made the
distinction clear to font designers.

LaTeX will need to be based on fonts that use Unicode extend with some
characters missing in Unicode.

Then if one wants to use a font with only one epsilon variation, then that
font will have to be mapped through the Unicode+ system that the extended
TeX/LaTeX systems is using, and via that mapping the missing glyph will
either substitute the right epsilon in a font already present, or produce
an error.

The mapping is this
          LaTeX -> Unicode+ TeX -> { Output fonts }
For the second mapping, one will have to make sure that:
  1. For every glyph in Unicode+ there is a default output.
  2. Every font that overrides the default mapping, will have to do that in
a prudent way, either by merely providing a new substitute glyph, or making
the use of some of the old glyphs impossible.

For sure, it is possible with such a system to map the two different
epsilons to the same output character, but it is not possibly in any type
of programming to make sure that the code is semantically sensible.

  Hans Aberg