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From: lee@anduk.co.uk (Liam R. Quin)
Newsgroups: comp.text
Subject: Re: What features would you like in GNU troff?
Message-ID: <26@nx32s.anduk.co.uk>
Date: 18 Jun 89 13:55:16 GMT
References: <JJC.89May31220314@jclark.UUCP> <742@dtscp1.UUCP> <10959@orstcs.CS.ORST.EDU> <21@nx32s.anduk.co.uk> <762@dtscp1.UUCP> <25@nx32s.anduk.co.uk> <13759@ncoast.ORG>
Reply-To: lee%anduk.uucp@ai.toronto.edu (Liam R. Quin)
Distribution: comp
Organization: Unixsys (UK) Ltd, Warrington, England
Lines: 52

In article <13759@ncoast.ORG> allbery@ncoast.ORG (Brandon S. Allbery) writes:
>As quoted from <25@nx32s.anduk.co.uk> by lee@anduk.co.uk (Liam R. Quin):
>| [...] ( and . are not possible in the first character of a [troff] name
>| nearly 100 names are pre-defined.  On the other hand, some control
>| characters are allowed....
>Beg pardon, but the only restriction I've found is that ( can not be used as
>a single-character name; it is possible to define a macro called ".F", for
>instance, and call it as "..F".

I was wrong, sorry.  You are not the only person to point this out.
The version of ditroff I checked originally had been hacked badly...
Even so, defining a number register or string whose name starts with a
dot is not a good idea, because all of the read-only number registers
do this (as in \n(.s, for example).
But the number of names you can have *is* limited, and not simply by
the name-space but by a built-in limit on the size of a (linear-searched)
symbol table.

>[...] I've not found a need to define "." as a
>macro, but it could be useful e.g. to monitor memory usage as you define
>macros, since troff will not only stop defining at .., it will execute the
>macro called "." if it exists; make "." do a ".pm" for a quick memory-usage
>debug check.  (Or ".rn pm .".)
No, you have to do
	.de xx .
to get this behaviour.

If you want it, I think I still have tmac.debug, and also a sed(?) script,
for tracing troff.  It monitors every nr/ds/de, and every call to every
user-defined macro (xx, say) prints
	.xx "a1" "" "" "" "" "" "" "" ""
or whatever.  I haven't needed it in a couple of years, as I now use a
version of troff that can print a much better debugging trace into the
intermediate file.

It's sometimes useful to define . and .. as macros if you are running a
version of troff that can print warnings, as pic tends to put out lines
starting with ..., and troff might say something like
	troff: pic.in: 34: warning call to undefined macro ".." ignored
The -mm package also uses some ``commenting conventions'' which involve
things that are not comments getting ignored, so it can be useful there,
too.

>++Brandon
Maybe I should be --Lee :-( :-(

Lee
-- 
Lee Russell Quin, Unixsys UK Ltd, The Genesis Centre, Birchwood,
Warrington, ENGLAND, WA3 7BH; Tel. +44 925 828181, Fax +44 925 827834
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