Page 357


Graham's notation correctly but perhaps too subtly conveys an important distinction between endp and null:

What's the difference? endp will signal an error if passed a non-list. null won't.

This actually makes endp a better test in most loops that step through a list, because it will catch non-lists immediately.

endp is a relatively recent addition to Lisp and is underutilized by almost everyone, including myself.