"Stephen J. Turnbull" <turnbull(a)sk.tsukuba.ac.jp&gt; writes: It's a documentation bug. I don't see why (concat "abc" '(120 377) [122]) would possibly return "abcxyz". when the number 377 does not correspond to the ASCII character ?y. Right. Since `concat' produces a string, all the list and vector elements are coerced to characters. The only coercion that makes sense for numbers is `int-char', and that should be documented. And yes, I'm aware that int-char is not the nicest function in the world, but within the bounds of XEmacs it makes sense and actually creates the least broken behaviour. For instance, this works both with and without Mule. (apply #'concat (mapcar #'list "Hrvoje Nikšić")) It could signal an error just as well. That's what I think it *should* do, anyway. Calling int-char is one thing; accepting numbers outside the available range and truncating them silently is another.