[TUHS] macro returning a value?

[Douglas McIlroy]

> Is there a trick to make a macro or string return a value?

I know what you mean. Though a string does return a value, it
can't compute an arithmetic result. Alternatively, a macro,
which can use arithmetic, can only return the result as a distinct
input line. (That might be overcome by a trick with \c, but I don't
see one right off.)

Though I have no useful advice about this dilemma, it does spur
memories. I wrote the pre-Unix roff that was reimplemented on
Unix and then superseded by Joe Ossanna's nroff. Joe introduced
macros. Curiously, I had implemented macros in an assembler so
early on (1959) that I have (incorrectly) been cited as the father of
macros, yet it never occurred to me to put them in roff.

Joe's work inspired me to add macros to pre-Unix roff. I did
one thing differently. A macro could be called the usual way or
it could be called inline like an nroff string. The only difference
was that a macro's final newline was omitted when it was
expanded inline. That implementation might have helped with
the dilemma.

Doug