Re: I must be going mad!

Josh Huber <huber(a)alum.wpi.edu&gt; writes: That defun is undefined behavior; it's not allowed to modify a constant list. Here is the correct version: (defun jmh-test-func () (let (tv) (setq tv (list (list ?a) (list ?b))) (push "testme" (cdr (assoc ?a tv))) tv)) What you did is in spirit similar to writing this C code: /* Return the string "foobar" with a one-character modification: */ foo(int ind, char c) { char *p = "foobar"; p[ind] = c; return strdup (p); } "foobar" is allocated only once, and so is '((?a) (?b)), at least in a compiled environment.