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

[Joel C. Salomon]

On Mon, Sep 24, 2012 at 5:18 PM, Michael Barr <barr at math.mcgill.ca> wrote:
> Well, going on a suggestion from someone, I can precede the loading with
> \let\LET\let and \let\DEF\def and follow it with \LET\let\LET and
> \let\def\DEF.  But isn't that all kind of silly?

Or use the \cs_set family of functions -- which are the same things,
renamed -- while taking advantage of the more readable boolean
expressions in Expl3.

Or don't, and LaTeX3 users will have to wrap `\input diagxy` with some
pre-packaged solution that restores the Plain csnames.

(Also, the Plain csnames are only undefined when LaTeX3 is built as a
format; when it's being used as the expl3 package it leaves those
names intact.)

--Joel