anchor.diff:            (destructuring-bind ((&rest args) &body body)
                 argument-forms
               (make-function args body env fenv)))
  -         (|function|
  +         (|fun|
             (destructuring-bind (name)
                 argument-forms
               ;; Sanity checks -- these should happen at "compile time"
  
positive.code:      (destructuring-bind (operator &rest argument-forms) form
  
         ;; Sanity check -- this should happen at "compile time"
         (unless (symbolp operator)
           (error "~A is not a valid operator name" (car form)))
  
         ;; Special operators
         (case operator
  
negative.code:             (unless (find-binding name fenv)
                (error "~A is not a lexically visible function" name))
              (lookup name fenv)))
           (|var|
            (destructuring-bind (name)
                argument-forms
              ;; Sanity checks -- these should happen at "compile time"
              (unless (symbolp name)
                (error "~A is not a valid variable name." name))
              (unless (find-binding name env)
                (error "~A is not a visible variable." name))
              (lookup name env)))
           (|bind-lexical-functions|
            (destructuring-bind (vars-and-funs &body body)
                argument-forms
  