anchor.diff:  		     :body-form
   		     (convert-implicit-progn body-forms new-environment)))))
   
  -;;; At the moment, this will never be used, because the form
  -;;; has been converted to a constant already, given that constantp
  -;;; returns true for something like (quote ...)
   (defmethod convert-special ((op (eql 'quote)) ast environment)
     (assert (= (length (subforms ast)) 2))
     (make-instance 'constant-form
  
positive.code:   ;; FIXME: issue a warning if the variable doesn't exist 
    (make-instance 'setq-form
  		 :original-form (original-form ast)
  		 :variable (lookup (original-form (car (subforms ast)))
  				   environment
  				   'variable)
  		 :value (convert (cadr (subforms ast)) environment)))
  
  (defmethod convert-special ((op (eql 'progn)) ast environment)
    (cond ((null (cdr (subforms ast)))
  
negative.code: 			    :value 
  			    (convert (if (typep binding-form 'symbol-form)
  					 nil
  					 (cadr (subforms binding-form)))
  				     environment)))))
        (loop for binding in bindings
  	    do (add-binding (name (variable binding))
  			    (variable binding)
  			    (variables new-environment)))
        (make-instance 'let-form
  		     :original-form (original-form ast)
  