# [texhax] Obsolete \centerline command used in amsbook class (Uwe L?ck)

Michael Barr barr at math.mcgill.ca
Sun Sep 23 14:50:11 CEST 2012

I would like to comment on Uwe Lueck's comments on the use of plain and
primitive tex commands in a latex document.  I once asked Leslie Lamport
how he felt about that (this was at least 20 years ago) and his reply was,
in effect, why not.

Yesterday, I had occasion to deal with a paper that had a number of
\newcommand{s} of the form
\newcommand{\un}[1]{\underline{#1}}
which isn't wrong, but a simple
\let\un\underline
would do the same thing more efficiently.  One thing that really irritates
me about amstex is that they have undefined some tex primitives.  One is
\over (and its relatives).  The late Michael Downes once explained to me
that this was because at the time it was being compiled tex didn't know
whether to do in in display, text, or script mode.  So \over in an amstex
document will lead to an error.  So how is frac implemented?  Well, I dug
down once and my recollection is that first they \let something else be
\over, then redefine \over to give an error message and then implement
\frac using the something else!  At best all you can say is that some
future implementation of some tex-like program might eliminate \over on
the grounds of efficiency.  But maybe not.  They might be loathe to render
millions of older papers obsolete.

About ten years ago I published a book that had several dozen matrices.  I
used the plain \matrix{...} which works perfectly well.  I never thought
that the AMS would publish it but that's who did.  I can imagine some poor
copy editor changing all the \matrix{...} to
\begin{matrix}...\end{matrix}.  Oh, I guess some script might do it
automatically.

And don't get me started on how much more functional \def is than
\newcommand.  I authored some diagram-drawing macros (a front end to
xy-pic, actually) some years ago and they would have been impossible to do
using \newcommand.  But when I use \def, someone is sure to comment that
that is not latex.  No, it is not, but when did latex turn into a
religion?

Which is not to say that latex doesn't provide lots of functionality that
plain doesn't.  But it remains, like the underlying tex engine, just a
tool.

Michael

--
The modern conservative is engaged in one of man's oldest exercises in
moral philosophy--the search for a superior moral justification
for selfishness.  --J.K. Galbraith