[nt]roff macros for ptx(1) output

[Henry Spencer]

ut-sally!riddle asked for macros to get decent-looking output from
the stuff ptx(1) puts out.  I'm posting this to a wider audience
because it is probably of wider interest.  After running into this
issue here, I added the following to our ptx(1) manual page:

	.SH EXAMPLE
	The following is a reasonably-minimal
	set of
	.I nroff
	statements which will format
	.I ptx
	output reasonably;  the style is similar to the index for this manual.
	The spacings may need adjustment for different output devices.
	.PP
	.RS
	.nf
	\&.de xx
	\&.if !""\\\\$1" \\\\$1\\fI\\a\\fR\\\\$2\\t\\\\$3\\fI\\a\\fR\\t\\\\$5
	\&.if !""\\\\$4" \\t\\\\$2\\t\\\\$3\\fI\\a\\fR\\\\$4\\t\\\\$5
	\&.if ""\\\\$1\\\\$4" \\t\\\\$2\\t\\\\$3\\fI\\a\\fR\\t\\\\$5
	\&..
	\&.nf
	\&.ta 3.7iR 3.95iL 7.65iR 7.8iR
	.RE
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry