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

[Alexander McCormmach]

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

(Please CC me with any reply because I am not subscribed to this list.)