Absolutely, or in the low bits of word aligned pointers as someone else mentioned above. Emacs Lisp is an example; here's its tagging apparatus. https://git.s

Absolutely, or in the low bits of word aligned pointers as someone else mentioned above. Emacs Lisp is an example; here's its tagging apparatus. https://git.savannah.gnu.org/cgit/emacs.git/tree/src/lisp.h#n207 https://git.savannah.gnu.org/cgit/emacs.git/tree/src/lisp.h#...