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Ulrik Vieth <[log in to unmask]>
Reply To:
Mailing list for the LaTeX3 project <[log in to unmask]>
Mon, 5 May 1997 11:29:32 +0200
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Joerg Knappen:

> Unfortunately, I think there is a point, where the math font encoding (here:
> MC) needs to be changed for the sake of compatibility.

> Currently it is possible and often applied practice, to use
> \( \mathit{\Gamma} \mathrm{\Gamma} \mathsf{\Gamma} \)
> to get the different shapes of the capital greek Gamma. The MC encoding as
> outlined by Justin Ziegler makes the capital Greek letter mathematical
> symbols (instead of mathematical letters) and treats them in a way entirely
> different from Latin letters. I cannot imagine any sensible implementation
> of \mathit and friends with the current MC encoding.

If I recall correctly, it was suggested very early in the discussions
in 1993 that additional math alphabets accessed with \mathxx{} that
require greek letters in addition to the roman letters would have to
be implemented as extra MC-encoded fonts (or a subset thereof), not
just extra T1 fonts.  The T1-encoded operator font (in \fam0) is just
for operator names (and possibly also for physical units), while it
is insufficient for \mathrm{} with arbitrary greek or roman letters.

Whether an MC- or T1-encoded font is needed to implement a specific
math alphabet might also depend on the context.  In a computer science
context, where you might just want to typeset keywords, variables or
strings in \mathbf{}, \mathit{} or \mathtt{}, it might be sufficent
to have T1-fonts.  In a physics context, however, where you might need
a full set of greek in upright, bold italics and bold sans oblique,
you'll obviously can't do without MC-encoded fonts.

In the case of \mathrm{} vs \mathnormal{} assuming that both are
implemented as MC-encoded fonts, this might imply some waste of
resources as the two sets of greek alphabets (upright and italics)
would appear in both fonts (possibly with the two sets exchanged).
However, this is probably not so much of a concern, as disk space
and memory is becoming cheaper every day.

If you really want to implement \mathrm{} with T1 + MC, you might get
along with a more involved macro definition as suggested by David.
I suppose, it shouldn't be too difficult to check for ASCII letters
in the macro argument with \ifcat and use the \fam mechanism for these,
whereas  the control glyph ligaturing mechanism might be employed for
anything else. (For bold/bold italics or sans bold/sans bold oblique,
several  extra T1 + MC combos could be used with the same mechanism.)

OTOH, it would be far more difficult to write a macro that just takes
care of handling lowercase greek specially, as would be needed with the
old math encodings.  While you can do an \ifnum comparison if you know
that the argument is a \mathchardef token, applying the comparison
to other tokens may cause syntax errors.  When I asked for suggestions
at one of Phil's macro writing tutorials, he suggested using \meaning
and handling all the possible cases, which seems like a lot of overhead.

Cheers, Ulrik.