[texhax] Correcting for math-mode kerning before commas and periods?

Alexander McCormmach alexander at tunicate.org
Fri Oct 14 15:05:26 CEST 2005

Hello all,

I'm wondering if it's possible to systematically correct for space that
TeX inserts after italicized letters in math mode. Such a correction is
needed in exactly those situations where one would *not* apply the
italics correction (\/), i.e., before commas and periods.

For example, the following puts way too much space between the
italicized "S" and the period:

  Let $U$ be the union of sets $R$ and $S$.

It looks a lot like it would if the end had been written:

  and {\it S\/}.

that is, with the italic correction, when rather it should look more
like it had been written:

  and {\it S}.

Is there any way to define a command which, when placed either just
before the period (or comma) or just inside the final "$", will
un-hskip or un-kern the unwanted space that TeX is inserting?

Here's another example taken from the second full sentence on page 442
of the TeXbook:

  The search looks first at character $a$ in scriptscriptfont $f$,
  if $C \le SS$; then it looks at $a$ in scriptfont $f$, if $C \le
  S$; then it looks at $a$ in textfont $f$.

The space TeX puts between the math-mode text and the *semicolons* is
desirable, but such correction is not desirable between all those $f$'s
and the commas or periods that follow them. How can those spaces be
gotten rid of? Any ideas?

Thanks ahead of time for your insights,

Alexander McCormmach

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