[plt-scheme] Swindle get-slot and set-slot methods?

From: Eli Barzilay (eli at barzilay.org)
Date: Sat Jan 21 02:42:24 EST 2006

On Jan 16, Will M. Farr wrote:
> Hello all,
> I'm curious if there's a way to have get-slot and set-slot methods in 
> swindle, as in the following example (this is very useful for wrapping 
> up an object which has an unusual data representation in a class which 
> provides a more standard way of accessing the underlying data):
> (defclass <complex> ()
>    x y (r :get [...] :set [...]) (theta :get [...] :set [...]))
> In this example, (slot-ref z 'r) would use the :get method, (slot-set! 
> z 'theta new-theta) would use the :set method, etc.  Of course, you can 
> do this if you only access the "fake" slots via the generic functions 
> (complex-r ...) and company, but it would be neat if this could be made 
> to work with the (with-slots ...) macros and (slot-ref ...).  Is there 
> a known way to do this cleanly?

No -- `with-slots' uses `slot-ref', which is a plain function.  I
thought about making it a generic, but that will be way too expensive
for something that is rarely useful.  Using getters and setters is a
much better solution.  The CLOS-like solution for this would be to
implement `slot-missing', which gives you a hook for playing such

          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                  http://www.barzilay.org/                 Maze is Life!

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