[plt-scheme] Macros which expand to uses of (call-next-method)

From: Will Farr (farr at mit.edu)
Date: Fri Jun 23 17:51:10 EDT 2006

Hey all,

I'm writing a macro which expands into a use of (call-next-method)
inside a (defmethod ...) from swindle:

(define-syntax define-binary-derivative
    (lambda (stx)
      (syntax-case stx ()
        ((_ f df/dx df/dy)
         (let ((cnm (datum->syntax-object #f 'call-next-method)))
               (defmethod (f (d1 <deriv>) (d2 <deriv>))
                 (with-slots d1 ((id1 'id) x dx)
                   (with-slots d2 ((id2 'id) (y 'x) (dy 'dx))
                     (if (eq? id1 id2)
                         (make <deriv>
                               :id id1
                               :x (f x y)
                               :dx (+ (* (df/dx x y) dx)
                                      (* (df/dy x y) dy)))
               (defmethod (f (d <deriv>) y)
                 (with-slots d (id x dx)
                   (make <deriv>
                         :id id
                         :x (f x y)
                         :dx (* (df/dx x y) dx))))
               (defmethod (f x (d <deriv>))
                 (with-slots d (id (y 'x) (dy 'dx))
                   (make <deriv>
                         :id id
                         :x (f x y)
                         :dx (* (df/dy x y) dy))))))))))

The system complains:

compile: bad syntax; reference to top-level identifier is not allowed,
because no #%top syntax transformer is bound in: call-next-method

If I don't introduce call-next-method with datum->syntax-object, I get
errors about call-next-method being undefined.  Is there *any* context
I can use to introduce call-next-method so that this works, or am I
just hosed?


Posted on the users mailing list.