anchor.diff:  
   (defvar *call/cc-returns* nil)
   
  -(defmacro with-call/cc (initial-environment &body body)
  +(defmacro with-call/cc (&environment e &body body)
     "Execute BODY with delimited partial continuations.
   
     Within the code of BODY almest all common lisp forms maintain
  
positive.code:   passed a continutaion. This object may then be passed to the
    function KALL which will cause execution to resume around the
    call/cc form. "
    (let ((walk-env nil)
          (evaluate-env nil))
      (assert (every (lambda (binding)
                       (and (consp binding)
                            (= 2 (length binding))))
                     initial-environment)
              (initial-environment)
              "Sorry, INITIAL-ENVIRONMENT must be a list of two element lists, not: ~S"
              initial-environment)
      (loop
         for (name value) in initial-environment
         do (setf walk-env (register walk-env :let name value)
                  evaluate-env `(register ,evaluate-env :let ',name ,value)))
      `(drive-cps (evaluate/cps ,(walk-form (if (rest body)
                                                `(progn ,@body)
                                                (first body))
  
negative.code:   (setf (symbol-value var) value)
    (kontinue k value))
  
  (defk k-for-local-lexical-setq (var env k)
      (value)
    (funcall (second (lookup env :lexical-let var :error-p t)) value)
    (kontinue k value))
  
  (defmethod evaluate/cps ((setq setq-form) env k)
    (cond
      ((lookup env :let (var setq))
       (evaluate/cps (value setq)
                     env `(k-for-local-setq ,(var setq) ,env ,k)))
      ((lookup env :lexical-let (var setq))
       (evaluate/cps (value setq)
                     env `(k-for-local-lexical-setq ,(var setq) ,env ,k)))
      (t
       (evaluate/cps (value setq)
                     env `(k-for-free-setq ,(var setq) ,env ,k)))))
  
  ;;;; SYMBOL-MACROLET
  
  