I am using aquamacs and latex mode, 'Symbol’s value as variable is void: last-command-char when trying to insert bracket' occurs when I am trying to insert a bracket.
How could I do, thank you
last-command-char was a variable made obsolete in Emacs-19.34 when it was replaced by
last-command-event (because in older Emacsen, events were only characters). It was finally removed in Emacs-24.
So some Elisp code you're using still refers to that variable and needs to be updated. Just
grep for that name in your files to see which thing needs to be updated.