継続とマクロでお手軽ブレークポイント - athosの日記 http://d.hatena.ne.jp/athos/20091226/p1 を #xyzzy + condition-restart で

gistfile1.cl

(require "condition-restart")


(define-condition breakpoint (condition)
  (name places)
  (:report (lambda (bp stream)
             (format stream "ぶれーく！ ~S" (breakpoint-name bp)))))

(defmacro bp (name &rest places)
  `(tagbody breakpoint
     (restart-case
         (signal 'breakpoint :name ',name :places '(,@places))
       (continue () :report "続行")
       ,@(mapcar (lambda (place)
                   `(,(intern (format nil "|~S|" place)) (#1=#:value)
                     :report (lambda (stream)
                               (format stream "~S => ~S を変更する"
                                 ',place ,place))
                     :interactive (lambda ()
                                    (list (condition-restart::read-value-for ',place)))
                     (setf ,place #1#)
                     (go breakpoint)))
           places))))

Common Lisp には break http://www.lispworks.com/documentation/HyperSpec/Body/f_break.htm があるのでいらない...