Node: compute-restarts, Next: , Previous: restart, Up: Conditions Dictionary



compute-restarts [Function]

compute-restarts &optional condition => restarts

Arguments and Values::

condition--a condition object, or nil.

restarts--a list of restarts.

Description::

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.

Examples::

      ;; 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~
          (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.
     
     

Affected By::

Existing restarts.

See Also::

find-restart , invoke-restart , restart-bind