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Path: utzoo!watmath!clyde!cbosgd!ihnp4!inuxc!pur-ee!uiucdcs!convex!kolstad
From: kolstad@convex.UUCP
Newsgroups: net.unix-wizards
Subject: Re: NROFF Question
Message-ID: <27300007@convex>
Date: Thu, 1-Aug-85 17:48:00 EDT
Article-I.D.: convex.27300007
Posted: Thu Aug  1 17:48:00 1985
Date-Received: Sat, 3-Aug-85 03:33:05 EDT
References: <707@rlgvax.UUCP>
Lines: 43
Nf-ID: #R:rlgvax.UUCP:-70700:convex:27300007:000:1006
Nf-From: convex.UUCP!kolstad    Aug  1 16:48:00 1985


you asked:

why does 
		.sp 4/2+1
not do the same as
		.sp 3
(in essence, anyway)

The answer is:

nroff (and troff) are always trying to be helpful and give you default
units for things.  When you say ".sp 1" then nroff (and troff, too)
say:  ``well, he doesn't want to space 1 UNIT (maybe 1/432" or 1/300")
he really wants to space 1 LINE (a VERTICAL UNIT -- 1v)''.  Now, this
is all well and good for things like ".sp 1+1" which translates to
".sp 1v+1v".  The trick comes when you do something like ".sp 4/2+1"
which good old nroff (and troff, too) changes to:

	.sp 4v/2v+1v

which is of course:

	.sp 2u+1v

which is a single space (or close enough)...

The solution to your problem is to remember two things:

(a) nroff & troff's only goal in life is to screw you
(b) when in doubt, ALWAYS SPECIFY UNITS.

The following seems to work just fine:

	.sp 4v/2u+1v

which is probably what you wanted anyway.

				Your friend in text processing,

					Rob Kolstad
					CONVEX Computers
					214-952-0351