How do I jump out of a function in Lisp?

Question

Is it possible in (Common) Lisp to jump to another function instead of call another? I mean, that the current function is broken and another is called, without jumping back through thousands of functions, as if I'd decide myself if tail call optimization is done, even if it is not the tail. I'm not sure if "(return-from fn x)" does, what I want.

Example:

(defun fn (x)
  (when x
    (princ x)
    (jump 'fn (cdr x)))
  (rest))

'jump' should be like calling the following function without saving the position of this function, instead returning to, where the original funcall was, so that there will be no stack overflow. 'rest' should only be executed if x is nil.

Answer 1

How about you use a tail call?

(defun fn (x)
  (if x
      (progn
        (princ x)
        (fn (cdr x)))
      (progn
        (rest))))

It calls fn in a tail position. If an implementation provides tail call optimization, you won't get a stack overflow. If you don't want to rely on that, you would need to handle the problem in a non recursive way. There are no explicit 'remove this functions stack frame and then call function X' operators in Common Lisp.