Add CALLBACK-FUNCTOR that allows the call back arbitrary functions

(in conjunction with make-annotated-callback)

scheme/httpd/surflets/callbacks.scm

@@ -1,5 +1,11 @@
 ;; Copyright 2002, 2003 Andreas Bernauer
 
+;; With callbacks you can create special links that are associated
+;; with a function. If the user clicks on the special callback link,
+;; the send-html/suspend won't return, but the function will be called
+;; instead. Note: It is not sensible to create callbacks on top level,
+;; as they contain continuations. You have to create a new callback
+;; every time you want to use it (inside a function).
 (define (make-callback function)
   (call-with-current-continuation
    (lambda (exit)
@@ -23,3 +29,7 @@ unexpected return values from website"))))))
 	 (callback (make-callback dispatch)))
     (lambda args
       (annotated-address callback args))))
+
+(define callback-functor
+  (lambda (req proc . args) 
+    (apply proc (cons req args))))