anchor.diff:  
   (defun highest-bang-var (form env)
     (let ((*warn-undefined* nil))
  -    (declare (special *warn-undefined*))
       (or
        (loop for var in (find-var-references (walk-form form nil (make-walk-env env)))
   	   if (bang-var-p var)
  
positive.code: that adds its two arguments."
    (declare (ignore subchar))
    (let ((body (read stream t nil t)))
      `(sharpl-expander ,body ,min-args)))
  
  (defun enable-sharp-l ()
    "Bind SHARPL-READER to the macro character #L.
  
  This function overrides (and forgets) and previous value of #L."
    (set-dispatch-macro-character #\# #\L #'sharpL-reader))
  
  (defun find-var-references (input-form)
    (typecase input-form
  
negative.code: ;;;; eliminate the 'boilerplate' LAMBDA and concentrate on the body of
  ;;;; the lambda.
  
  (defmacro sharpl-expander (package body min-args &environment env)
    (let* ((form body)
           (lambda-args (loop
                           for i upfrom 1 upto (max (or min-args 0)
                                                    (highest-bang-var form env))
                           collect (make-sharpl-arg package i))))
      `(lambda ,lambda-args
         , (when lambda-args
             `(declare (ignorable ,@lambda-args)))
  