[goops] adding a number class with generic methods

["Marco Maggi" <marco.maggi-ipsu@poste.it>]

Hi,

  I  am trying  to add  a new  number class,  export generic
methods from a module and import them into another one. If I
ignore the GOOPS tutorial and read only the reference, it is
my understanting that I should do:

;; ----------------------------------------
;; exporting.scm

(define-module (gee gmp ompfr)
  #:use-module (oop goops)
  #:use-module (gee gmp mpfr))

(define-class <mpfr> (<number>)
  (n #:init-value (real->mpfr 0) #:init-keyword #:value))

;; ... other stuff ...

(define-method (= (a <mpfr>) (b <mpfr>))
  (mpfr-equal? (slot-ref a 'n) (slot-ref b 'n)))

(define-method (= (a <mpfr>) (b <real>))
  (mpfr-equal? (slot-ref a 'n) (usable->mpfr b)))

(define-method (= (b <real>) (a <mpfr>))
  (mpfr-equal? (slot-ref a 'n) (usable->mpfr b)))

(export =)

;; ----------------------------------------
;; importing.scm

(define-module (my-test)
  #:use-module (mmg test dotest-1)
  #:use-module (oop goops)
  #:duplicates merge-generics
  #:use-module (gee gmp ompfr))

(= #,(MPFR 2) #,(MPFR 2))

;; ----------------------------------------

but I get this error:

...
   ?: 6  (= #<<mpfr> 40351520> #<<mpfr> 403505e0>)

<unnamed port>: In expression (= #<<mpfr> 40351520> #<<mpfr>
403505e0>):
<unnamed port>: Unbound variable: =


  If I read the tutorial it seems that I have to replace the
'(define-method (= ...' definitions with:

;; ----------------------------------------

(define-generic my=)

(let ((original= =))

  (define-method (my= (a <number>) (b <number>))
    (original= a b)))

(define-method (my= (a <mpfr>) (b <mpfr>))
  (mpfr-equal? (slot-ref a 'n) (slot-ref b 'n)))

(define-method (my= (a <mpfr>) (b <real>))
  (mpfr-equal? (slot-ref a 'n) (usable->mpfr b)))

(define-method (my= (b <real>) (a <mpfr>))
  (mpfr-equal? (slot-ref a 'n) (usable->mpfr b)))

(set! = my=)

;; ----------------------------------------

but I get the same error.

  I do not understand why  the first solution does not work;
I've tried different combinations  of functions but there is
something I am missing.



--
Marco Maggi

"They say jump!, you say how high?"
Rage Against the Machine - "Bullet in the Head"



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