Path: utzoo!mnetor!uunet!husc6!wjh12!bb
From: bb@wjh12.harvard.edu (Brent Byer)
Newsgroups: comp.text
Subject: Re: pic bug (not quite)
Message-ID: <197@wjh12.harvard.edu>
Date: 15 Apr 88 16:33:49 GMT
References: <921@hsi.UUCP>
Reply-To: bb@wjh12.UUCP (Brent Byer)
Organization: Textware Intl., Cambridge MA
Lines: 53
Keywords: pic

In article <921@hsi.UUCP> stevens@hsi.UUCP (Richard Stevens) writes:
>I've encountered the following bug in pic, and was wondering if
>anyone has a fix.  I'm using the pic that came with DWB 2.0.
>
>Arrows in pic that go straight down or straight up have the head
>of the arrow shifted slightly to the left.  For example,
>
>         |                               |
>         |                               |
>       \ | /                            \|  /
>        \|/                              \ /
>
>      correct           this is what the bug produces (exaggerated)

 ( I believe you will find the glitch factor to be even worse
   on angled shafts. )
The bug is not really in pic; anal analysis of pic's output
will show it to be correct.  So, the problem is actually
in some combination of ditroff and your post-processor.

>The bug appears to be in the latest AT&T Release (i.e., DWB 2.0),
>as I've found, [see also p. 345 of Bach "The Design of the UNIX
>Operating System"] but was fixed sometime in Version 8 [see p. 313
>of Kernighan and Pike for the bug, but see also p. 111 of Bentley's
>"Programming Pearls" for a fixed version] and is fixed in Version 9
>[see p. 173 of "The AWK Programming Language" by A. K. and W.].

The above observations appear valid, but because of the *actual*
nature of the problem, it may very well not have been fixed at all.

>Does anyone have a fix ??  Thanks.

Since Textware endeavors to deliver high-quality software to a
hopefully fussy audience, we have fixed this (and quite a few
other pic-related doo-dahs) in our Tplus product.  Remember, just
because a vendor *advertises* "full support for pic" doesn't mean they
are capable of delivering.

It's because of this tighter-than-you-thought inter-relationship of
{ pre-processors, formatter, and post-processor } that we recommend
that users get the entire set-up from a single (binary?) source.
Otherwise, support for a problem like this can be a futile nightmare.

> Richard Stevens
> Health Systems International, New Haven, CT { uunet | ihnp4 } ! hsi ! stevens

	Brent Byer   { ihnp4!ihesa , harvard!cca } !textware!brent
	Textware Intl.
	PO 14 - Harv Sq
	Cambridge, MA 02238
	  (617) 864-8398 (uni-text)

	"Leaners don't count, in typesetting."