I want to let the command \old| refer to the command \| (which produces the output ||.) So I do:
\old|
\|
||
\let\old|\|
LaTeX complains "Missing $ inserted." How can I fix it?
\def\old#1{\|}
\<one-char>
\<arbitrary-number-of-letters>
|
\let\oldvert\|
\def\old#1{\|}and than you can work with\old|– Marco Daniel Mar 02 '13 at 20:01\<one-char>or\<arbitrary-number-of-letters>. The character|is not a letter. I suggest using\let\oldvert\|. – yo' Mar 02 '13 at 20:04