# Miscellany

• To: math-font-discuss@cogs.susx.ac.uk
• Subject: Miscellany
• From: jeremy@cs.aukuni.ac.nz (Jeremy Gibbons)
• Date: 06 Aug 1993 14:30:02 +1200

Gosh, we have been busy. I've just got round to catching up on 38 messages
on math fonts. A few odd comments:

> 1 - It is my understanding that new encoding schemes are being
> planned to accomodate the usage of calligraphic, fraktur and
> blackboard letters in math formulas, and that these will
> have to be assigned to distinct families (6 in all). I believe
> this is a serious mistake. Many PostScript fonts are available
> for calligraphic, script and fraktur typefaces and these can
> be used in math instead. The advantage of this is that
> one does not have to waste many fonts even if they may never
> used in a particular document.

I'm not sure whether I've understood Sami correctly, but I take him to be
saying, "don't assign standard families to fraktur etc, because families
are scarce and fraktur rarely used". Imho, there should be a "standard"
scheme for replacing one family with another---instead of \newfam (or
\new@mathgroup? in NFSS), it should be possible to define a macro \reusefam
that, for example, takes the name of a family and uses that if possible;
otherwise it does a \newfam (or perhaps gives an error). Thus, I could say

\reusefam\frakfam\myfam

to assign \myfam as a "new" family, overriding \frakfam. Then you can
assign the sixteen most popular families as standard, and macro packages
can override whichever they don't expect to use.

This must surely be an argument for (as I presume is the intention)
regrouping all the symbols so that they are more logically arranged. For
example, when I use CM I use the text italic for maths identifiers, but I
can't wheel out the math italic fonts because they contain odd symbols that
I want to use. Knuth's encoding is not at all modular.

> knuth's distinction between math italic and text
> italic is also an improvement that is not fully appreciated.  it is
> very tedious, if not necessarily difficult, to determine the metrics
> and build virtual fonts out of "ordinary" italic that can be used to
> set math in an intelligible and unambiguous manner.

But there's more to the difference between cmmi and cmti than interletter
spacing. Just look at lowercase "a"; its shape changes too. Why?
Dispensible historical reasons, or still-relevant technical ones?

> >>A font made for maths does not have the same adjustments as a font made for
> >>text.
>
> >I always thought it was OK to use \rm \it \sf etc in math. Are you
> >telling me I shouldn't have?
>
> The problem is that the subscript and superscript positioning isn't great
> when the nucleus is taken from a text font, because of the bizarro way
> that Appendix G uses horizontal escapement and italic correction to
> indicate script positioning.  Anyone can use any font they like in math
> mode, but you're not guaranteed wonderful results.  (Take a look at
> $\Gamma_0$ for example.)

This may be off topic, but anyone's observations on how to turn a text
italic font into a suitable math italic one would be most welcome. How does
App G's usage of fontdimens differ from the "expected" usage?

I've been using Lucida Bright for several months, and quite like it. I use
the text italic for maths, because my identifiers tend to be
multi-letter. But then I occasionally get odd positioning of subscripts and
so on. What should I do? (The right answer is presumably to spend half a
day playing with them, but that isn't on the cards at the moment... :-( so
if anyone has already done so, please let me know!)

> Here is a list of new symbols that *could* be included in the new encoding.
> Any comments are welcome. If you happen to know that some of the symbols
> are very much need, please say so. If you know where th metafont code can
> be found please say so. If you know of some fonts that actually have them
> please say so.
[...]
>   \item Dijkstra choice: $[\!]$

In St Mary's Rd (three to choose from!).

>   \item Semantic brakets $[\![$ and $]\!]$ must be extensible.

In Alan's cspex. Also in Lucida Bright (but that's probably not much use).

>   \item The double circled integral, or the surface integral for
>     physicists.
>   \item A single integral with on top a $\Sigma$:
>     $\displaystyle\int\!\!\!\!\!\!\textstyle\Sigma$ (J\"org)
>   \item A single integral with a slanted dash:
>     $\displaystyle\int\!\!\!\!\!\textstyle-$
>   \item A triple, circled integral.

Lots of integrals in Lucida Bright, again.

>   \item A sigma with a long tail that goes a little bit below the
>     baseline.

Surely that's a text Greek symbol?

> I've realized we
> really need an `arrow building kit', which is something I'm still kicking
> ideas around for.  I'll post once I've got something coherent to say!

Mike Spivey's "oxsy" font (now superseded by fuzz) contains macros for
building arrows. Not sure whether it's PD, though.

>   \item Possibly something like $\bar($ and $\bar)$ if the bar was
>     touching, maybe called banana brackets.
>
> These aren't banana brackets!  Banana brackets look (sort of) like $(\!|$
> and $|\!)$.  Or they look like bananas if you believe Jeremy...

Bananas are different in NZ. (Well, no, they're not, but cucumbers are.
Really! They're short, stubby and straight, not long, slender and curved.
But I digress...)

I'm not convinced that banana brackets are useful to sufficiently many
people. Though it must be said, they have appeared in print in several
places. If you really want to go OTT, you could include lenses ($[\!($ and
$)\!]$) and barbed wire ($\overlay{[}{\langle}$ and
$\overlay{\rangle}{]}$), which appear (with double square brackets, called
"envelopes", and banana brackets) in Meijer et al, "Functional Programming
wuth Bananas, Lenses, Envelopes and Barbed Wire" (LNCS 523, eg p131).

>   \item Must not forget the three versions of the \# hash sign. I
>     believe some are geometric, and some aren't.
>
> For those who are wondering, those are the slanted hash sign, the upright
> hash sign, and the musical sharp sign (which isn't a hash sign at all!)

Musical "sharp" sign should go in a text symbol font, not a math symbol
font.

Do people really use slanted hash and upright hash to mean different
things, or do they only use one, picking whichever happens to be available?

Jeremy