Couldn't just define <square> like this: (define-class <square> (<rectangle>))
then define a side method: (define-method (side (@ <square>)) (slot-ref @ 'height)) This way, you're not storing the same information twice. On 22 July 2014 14:18, Marko Rauhamaa <ma...@pacujo.net> wrote: > > Consider this simple program: > > ======================================================================== > (use-modules > (oop goops) > (ice-9 optargs)) > > (define-class <rectangle> () > (width #:accessor width #:init-keyword #:width) > (height #:accessor height #:init-keyword #:height)) > > (define-method (area (@ <rectangle>)) > (* (height @) (width @))) > > (define-class <square> (<rectangle>) > (side #:accessor side #:init-keyword #:side)) > > (define-method (initialize (@ <square>) args) > (let-keywords > args #f ((side #f)) > (next-method @ (list #:width side #:height side)))) > > (format #t "~S\n" (area (make <square> #:side 3))) > (format #t "~S\n" (side (make <square> #:side 3))) > ======================================================================== > > The program outputs: > > ======================================================================== > 9 > ERROR: Unbound slot in object #<<square> b76cfec0> > ======================================================================== > > I understand that by overriding <square>'s initialize method I'm losing > the magic of the default initializer. How could I have the cake and eat > it, too? > > > Marko > >
