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accessor with 2/3 parameters
From: |
Marco Maggi |
Subject: |
accessor with 2/3 parameters |
Date: |
Fri, 18 Aug 2006 20:35:45 +0200 |
Ciao,
I wanted to create an accessor called ELM with synopsis:
(set! (elm obj key) value)
(elm obj key)
which is the same required by the VECTOR-SET! and
VECTOR-REF pair. For this both the #:accessor
keyword of class definition and the explicit
definition:
(define-method (elm (obj <my-class>) key) ...)
(define-method ((setter elm) (obj <my-class>) ...) ...)
do not work. I had to use:
(export elm)
(set! elm (ensure-accessor
(make-procedure-with-setter
(lambda (o key)
...)
(lambda (o key value)
...))))
So a working example is:
;; ----------------------------------------
(use-modules (oop goops))
(debug-enable 'debug)
(debug-enable 'backtrace)
(debug-enable 'trace)
(define-class <my-vec> ()
(v #:init-keyword #:value))
(define elm (ensure-accessor
(make-procedure-with-setter
(lambda (v k)
(vector-ref (slot-ref v 'v) k))
(lambda (v k value)
(vector-set! (slot-ref v 'v) k value)))))
(define-method (display (o <my-vec>) (port <port>))
(display (slot-ref o 'v) port))
(define v (make <my-vec> #:value #(1 2 3)))
(set! (elm v 1) -9)
(display v)(newline)
(display (elm v 0))(newline)
(display (elm v 1))(newline)
(display (elm v 2))(newline)
;; ----------------------------------------
I do not like it because ELM does not know about
<my-vec>, but at least ELM is a generic function.
Is there a better way to do it?
If there is a solution it could be a good idea to
add the implementation example to the GOOPS
documentation.
--
Marco Maggi
"They say jump!, you say how high?"
Rage Against the Machine - "Bullet in the Head"
- accessor with 2/3 parameters,
Marco Maggi <=