My old way of redefining a command no longer works.

[Steve Litt]

Hi all,

For years when wanting to redefine \whatever, I've done:

\let\oldwhatever = \whatever
\def\whatever{\whatever\newstuff}

But now the following doesn't work:

=====================================
\let\oldbeginsection=\beginsection
\def\beginsection{\oldbeginsection}
\bye
=====================================

The preceding code yields the following error:

#####################################
[slitt at mydesk plaintex]$ ./jj
rm: cannot remove 'junk.pdf': No such file or directory
This is LuaTeX, Version 1.17.0 (TeX Live 2023) 
 restricted system commands enabled.
(./junk.tex
Runaway definition?
->
! Forbidden control sequence found while scanning definition of
\beginsection. <inserted text> 
}
<to be read again> 
\oldbeginsection 
l.2 \def\beginsection{\oldbeginsection
                                    }
? 
#####################################

Anyone know why the preceding code yields the preceding error?

Thanks,

SteveT

Steve Litt 
Autumn 2022 featured book: Thriving in Tough Times
http://www.troubleshooters.com/bookstore/thrive.htm