[plt-scheme] 299.105

At Sun, 8 May 2005 20:41:51 +0200, Erich Rast wrote:
> ==> serialize: expects argument of type <serializable object>; given 
> #<procedure:43:2>

The procedure on line 43 is `add-key', and procedures aren't
serializable.

Probably you meant for it to be a private method instead of a private
field, and the same for `remove-key'. Changing the definitions to

   (define/private (add-key key)
     (set! keys (append keys (list key))))

   (define/private (remove-key key)
     (set! keys (remove key keys)))

allows serialization to proceed.

Matthew