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From: marcel@cs.caltech.edu (Marcel van der Goot)
Newsgroups: comp.text.tex
Subject: Re: TABLES-- Alligning the decimal points.
Summary: Knuth's fix
Message-ID: <1991Jan31.041733.18119@nntp-server.caltech.edu>
Date: 31 Jan 91 04:17:33 GMT
References: <1991Jan25.114530.2289@vax5.cit.cornell.edu> <1991Jan26.221417.24115@Neon.Stanford.EDU> <NICKSON.91Jan30142422@circa.comp.vuw.ac.nz>
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There have been quite some postings concerning alignment of decimal
points, with more and more complicated macro sets. (Nothing wrong
with that.) However, in the TeXbook Knuth gives a simple solution
(well, it's more a "fix") to the problem.
Quoting:

> This isn't especially pleasing to the eye, but that's what
> people do, so you might have to conform to the practice.
> [...]
> But the author usually prefers to use another, less sophisticated
> method, which takes advantage of the fact that the digits 0, 1, ..., 9
> have the same width in most fonts: You can choose a character that's
> not used elsewhere in the table, say `?', and change it to an active
> character that produces a blank space exactly equal to the width of
> a digit. Then it's usually no chore to put such nulls into the table
> entries so that each column can be regarded as either centered or
> right-justified or left-justified. For example. `??0.2010' and
> `297.1???' have the same width, so their decimal points will line up
> easily. Here is one way to set up `?' for this purpose:
> 
> 	\newdimen\digitwidth
> 	\setbox0=\hbox{\rm0}
> 	\dgitwidth=\wd0
> 	\catcode`?=\active
> 	\def?{\kern\digitwidth}
> 
> The last two definitions should be local to some group, e.g., inside a
> \vbox, so that `?' will resume its normal behavior when the table is
> finished.

This is indeed not very elegant, but simple and reliable.

                                          Marcel van der Goot
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