Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!sdd.hp.com!spool.mu.edu!uunet!mtxinu!jaap
From: jaap@mtxinu.COM (Jaap Akkerhuis)
Newsgroups: comp.text
Subject: Re: In troff, is "|" supposed to be slanted in Italic?
Summary: Are Italic telephone poles slanted? Is the tower of Pisa Italic?
Message-ID: <1991May9.000730.23509@mtxinu.COM>
Date: 9 May 91 00:07:30 GMT
Article-I.D.: mtxinu.1991May9.000730.23509
References: <1470@ecicrl.ocunix.on.ca> <1991May6.152022.28260@cbnewsl.att.com>
Reply-To: jaap@mtxinu.COM (Jaap Akkerhuis)
Organization: mt Xinu, Berkeley
Lines: 62

First some background:

Someone complained that vertical lines came out slanted in eqn when he
wasn't expecting it.

In article <1991May6.152022.28260@cbnewsl.att.com> npn@cbnewsl.att.com (nils-peter.nelson) writes:
 > 
 > 
 > In fixing up xditview, this was the one "bug" I couldn't
 > solve. eqn | troff | xtv     will display piles with
 > slanted lines. Brian Kernighan (author of pic) insists
 > italic applies to letters only; X persistently slants
 > *all* characters in the Italic fonts. Brian says he may
 > try to change pic not to assume Italic is safe for
 > non-letters, but no promises.
 > I had to put shameful fudges in to get square roots,
 > table corners and brackets to align, because of
 > similar disagreements between X, PostScriptt and troff.

Remember good old troff? Just four fonts with very limited amount
of characters.  So basically old the special characters were taken
from the special fonts.

Eqn was/is relying on this fact. Just switching on the italic font
(and silently assume it is on position two) for the bulk of the
work and then rely on picking the special characters from the
special font.

Is is a bug in eqn? Well, I'm not sure. Let us first ask ourself,
what a vertical bar actually supposed to be if it is italic? Should
it be slanted?

I can easely defend that a vertical bar should be a vertical bar
whether the font is italic or not. If we want a slanted bar we have
the slash character (/) anyway. So the behaviour of eqn is right.
The font is wrong. Just get the | mapping to a slanted line out of
the font descriptions and things will be dandy.

Of course, one could be stubborn and argue that, since the italic
font slants, the vertical bar should be slanted, just to be
orthogonal. Eqn maps the paranthesis to roman when encountered, so
it could do the same.  However, I can easier see the reason for
the paranthesis than a vertical bar. If I want a vertical bar, that
is what I want, if I want a slash, I'll ask for it.

It looks like I agree with Brian, so I would recommend to go for
the first solution. Fix those font description files! Wipe out the
definition for the vertical bar!

It is amazing how often people take the font description files for
granted, without giving it any thought.  There is some implied
semantics attached to these files. Not only to what makes sense to
troff to have in it for a particular font, it also applies to the
form of the characters, like how much white there is around the
line drawing characters used in \l'' && \L'' requests etc. If the
characters don't work properly, fix the font definitions and/or the
back-end!

	jaap

PS. I seem to remember that Brian had something to do with eqn as
    well :-)