Rik Kabel schrieb am 20.11.2020 um 00:18:
You are right about not quite understand.
There are cases where you want to pass a command to another command as
it is without replacing it with its content, e.g. when you store the
\TeX logo in the table of content the \TeX command should be written in
the register and not the content of the command.
In the following example the first line prints the definition of the
\TeX logo but in many cases you ant to preserve the command as in the
second line.
\starttext
\tex{TeX} = \detokenize\expandafter{\TeX}
\blank
\tex{TeX} = \detokenize{\TeX}
\stoptext
To make it easier to keep the command eTeX added a new command
\protected which can be used before \def to achieve this (ConTeXt
provides the same thing under the name \unexpanded).
The following example shows how you can use \protected\def to keep
always the current meaning of \foo when you print the content of \bar.
\starttext
\def\foo{foo}
\edef\bar{\foo}
\def\foo{bar}
\startlines
bar=\bar
foo=\foo
\stoplines
\blank
\protected\def\foo{foo}
\edef\bar{\foo}
\protected\def\foo{bar}
\startlines
bar=\bar
foo=\foo
\stoplines
\stoptext
A problem in older TeX engines is that \csname ...\endcsname didn't
respect this protection and replaced the protected command with its
content, recently Hans changed this behavior in LMTX which lead to the
error message in your document.
Does this mean that I can have the same definitions in MkIV and LMTX
(after some future update), or should I hunt down the \defines in both,
or that I should fork (or mode test) my source environment files, one
set for LMTX and one for MkIV?
When you use \define to store arguments which are passed as arguments to
other command you have to change this to \defineexpandable but its best
to do this in MkIV and LMTX because protected commands are the wrong
thing in this case. Even though it would work in MkIV in some cases you
run into problems when you pass argument to Lua.
Wolfgang
___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the
Wiki!
maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage : http://www.pragma-ade.nl / http://context.aanhet.net
archive : https://bitbucket.org/phg/context-mirror/commits/
wiki : http://contextgarden.net
___________________________________________________________________________________
