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From: leff@.seas.smu.edu (leff)
Newsgroups: comp.text
Subject: troff string register interpolation if strange char
Message-ID: <16321@smunews.UUCP>
Date: 1 Jun 90 20:41:11 GMT
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Reply-To: leff@.seas.smu.edu (leff)
Organization: Southern Methodist University, CSE Dept. Dallas, TX
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A strange control character is being inserted on character interpolations
before a closing \} of an if statement.

In the example below, there are two operations involving interpolation of a
string register before a \} of an if.  In the first operation, the output of 
the "tm" inside of the macro, M1, includes both an X and a control character.

The second operation shows that the string register X2 receives both an X
and a control character.  

I have experienced this problem with both nroff and ditroff.

nroff inserts an octal 36 (^^) while ditroff inserts a control-Q.

The obvious workaround is to insert a dummy statement just before the \}
but I would like to understand what is happening.  Any ideas?

.de M1
.if X\\n(R1X1X \{\
.tm \\*(U1\}
.if X\\n(R1X1X \{\
.ds X2 \\*(U1\}
..
.ds U1 X
.nr R1 1
.M1
.tm \*(X2X
 Laurence Leff, Ph.D               |A job is like sex, when you do it for money
CS,SMU, Dallas, Texas 75275-0122,  |You take away all the fun.
Phone: 214-692-3459 Moderator comp.doc.techreports/TRLIST, Symbolic Math List 
 convex!smu!leff leff%smu.uucp@uunet  E1AR0002 at SMUVM1 (BITNET)