Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!uwvax!umn-d-ub!umn-cs!timbuk!anne
From: anne@timbuk.cray.com (Anne Chenette)
Newsgroups: comp.text
Subject: Ditroff question: what does \X do?
Summary: Is this message making it to your site?
Keywords: PostScript weirdness
Message-ID: <5769@timbuk.cray.com>
Date: 16 Nov 89 21:44:40 GMT
Organization: Cray Research, Inc., Mendota Heights, MN
Lines: 62

I've had a weirdness happen with ditroff/PostScript.  A user mistakenly
left out the space when he wanted the '\ ' (backslash-space) escape
sequence; the results were most unexpected.  Can anyone explain
what is happening?  (I hope news doesn't eat my \ characters!)

The following sequence in a ditroff source file:
	\s-1\%CRAY\ Y-MP\s+1, \s-1\%CRAY\X-MP\ EA\s+1, and
	\s-1\%CRAY\ X-MP\s+1 systems,
generates the following PostScript code:
	3369(CRAY)X
	3621(Y-MP)X
	11 s
	3833(,)X
	10 s
>	3880(CRAY)X			< Suspicious-looking
>	MP EA, and			< code here
	11 s
	4135(-)X
	10 s
	1890 5418(CRAY)N
	2142(X-MP)X
	11 s
	2379(systems,)X
which causes the following message from PostScript:
	Error: undefined; OffendingCommand: MP
	Flushing: rest of job (to end-of-file) will be ignored

What did I do???  Is \X a ditroff escape sequence?  If so, how is it used?
I'd like to include PostScript figures in a ditroff document; can \X
(or anything else) be used to do it?  How do I get back to ditroff once
I "escape" to PostScript?  Is any of this documented anywhere?  By the by,
I'm running SunOs 3.5 with DWB ditroff (version unknown).

I don't have ditroff documentation, other than the ditroff(1) man page;
and my troff bible (J. Ossana, RIP) does not list the escape sequence \X
(backslash-X).  Worse yet, I don't know PostScript (mea culpa!)

I would be grateful for any and all information.  Please send mail,
if possible; our news feed is flakey.

			Thanks in advance,
			  Anne Chenette
			    anne@cray.com
			      or
			    ..!uunet!cray!com

P.S.  In case the ditroff output is important, here it is (for the
      relevant passage).  The ditroff output ends shortly after
      this occurs (about 75 lines later).

	76C58R58A58Y56 22Y56-27M76Ps11
	53,ws10
>	47C58R58A58Ywx X MP EA, and		< This also looks suspicious
	s11
	h81Chy
	n104 0
	H374
	s10
	V5418
	h1516cC
	58R58A58Y56 22X56-27M76Pws11
	78s41y47s41t34e44m78s41,