condition—a condition object, or nil.
restarts—a list of restarts.
compute-restarts uses the dynamic state of the program to compute
a list of the restarts which are currently active.
The resulting list is ordered so that the innermost (more-recently established) restarts are nearer the head of the list.
When condition is non-nil, only those restarts
are considered that are either explicitly associated with that condition,
or not associated with any condition; that is, the excluded restarts
are those that are associated with a non-empty set of conditions of
which the given condition is not an element.
If condition is nil, all restarts are considered.
compute-restarts returns all
applicable restarts,
including anonymous ones, even if some of them have the same name as
others and would therefore not be found by find-restart
when given a symbol argument.
Implementations are permitted, but not required, to return distinct
lists from repeated calls to compute-restarts while in
the same dynamic environment.
The consequences are undefined if the list returned by
compute-restarts is every modified.
;; One possible way in which an interactive debugger might present
;; restarts to the user.
(defun invoke-a-restart ()
(let ((restarts (compute-restarts)))
(do ((i 0 (+ i 1)) (r restarts (cdr r))) ((null r))
(format t "~&~D: ~A~%" i (car r)))
(let ((n nil) (k (length restarts)))
(loop (when (and (typep n 'integer) (>= n 0) (< n k))
(return t))
(format t "~&Option: ")
(setq n (read))
(fresh-line))
(invoke-restart-interactively (nth n restarts)))))
(restart-case (invoke-a-restart)
(one () 1)
(two () 2)
(nil () :report "Who knows?" 'anonymous)
(one () 'I)
(two () 'II))
▷ 0: ONE
▷ 1: TWO
▷ 2: Who knows?
▷ 3: ONE
▷ 4: TWO
▷ 5: Return to Lisp Toplevel.
▷ Option: 4
→ II
;; Note that in addition to user-defined restart points, COMPUTE-RESTARTS
;; also returns information about any system-supplied restarts, such as
;; the "Return to Lisp Toplevel" restart offered above.
Existing restarts.