anchor.diff:                 (error "No binding for ~A in or above ~A" symbol env)))
         (error "No binding for ~A in or above ~A" symbol env)))
   
  -(defmethod clutter-bound? (symbol (env env))
  +(defun clutter-bound? (symbol &optional (env *global-env*))
     (if env
         (if (nth-value 1 (gethash symbol (env-bindings env)))
             t
  
positive.code: 
  (declaim (optimize debug))
  
  (defclass env ()
    ((parents :accessor env-parents :initarg :parents)
     (bindings :accessor env-bindings :initarg :bindings :initform (make-hash-table :test 'eq))))
  
  (defgeneric lookup (symbol env))
  (defgeneric (setf lookup) (new-value symbol env))
  (defgeneric extend (symbol env &optional value))
  
  (defun make-env (&rest parents)
    (make-instance 'env :parents parents))
  
  (defmethod print-object ((o env) s)
    (print-unreadable-object (o s :type t :identity t)
  
negative.code:             t))
        nil))
  
  (defun extend (env symbol &optional value)
    (assert (clutter-symbol-p symbol))
    (unless (eq symbol *ignore*)
      (when (nth-value 1 (gethash symbol (env-bindings env)))
  