bug#37461: define-generic doesn't promote equal? to generic

[Mikael Djurfeldt]

Hi Rob,

I left GOOPS development at Guile version 1.8. The way this was then intended to work was that

  (define-generic equal?)

means that you want to create a new generic equal?. This discards the old binding for equal?.

  (define-method (equal? (a <string>) (b <string>)) ...)

on the other hand, means that you want to *extend* the current behavior of equal? with a specialization to two strings. The method is then added to equal?, which in guile-1.8 was from scratch a "primitive-generic".

Here's the actual output of guile-1.8:

guile> equal?
#<primitive-generic equal?>
guile> (use-modules (oop goops))
guile> (define-method (equal? (a <string>) (b <string>)) (string=? a b))
guile> equal?
#<primitive-generic equal?>
guile> (primitive-generic-generic equal?)
#<<generic> equal? (2)>
guile> (define-generic equal?)
guile> equal?
#<<generic> equal? (0)>

I don't know if the changes between 1.8 and 2.2.6 is intentional or a bug. Does someone here know?

Best regards,

Mikael

On Sat, Sep 21, 2019 at 7:09 PM Rob Browning <address@hidden> wrote:

Rob Browning <address@hidden> writes:

> A re-export doesn't affect the module using the re-exporter, and export
> and replace both fail with "Unbound variable: equal?", even though
> there's a (define equal?  ...)  in the module.

Perhaps there was something else going on, but now :replace does appear
to work, e.g. if I define a completely new generic and then

  (define equal? new-equal)

a "replace: (equal?)" in the define-module does appear to work when you
use the module.

Though define-method still ignores attempts to specialize (or change the
specialization) for existing types like <string>, etc. (as mentioned in
my other message).

Thanks
--
Rob Browning
rlb @defaultvalue.org and @debian.org
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