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Does anyone have an applicable struct example

From: Tristan Colgate
Subject: Does anyone have an applicable struct example
Date: Fri, 25 Jun 2010 10:14:06 +0100

Hi all,

  I'd like to make use of the applicable structs feature but am
running into problems.

>From what I can gather from the release note that mentions it, the
following should work,
instead, I get a segfault.

scheme@(guile-user)> (define <mything-vtable> (make-struct
<applicable-struct-vtable> 0))
scheme@(guile-user)> (define mything (make-struct <mything-vtable> 0
(lambda()(display "some code")(newline))))
Segmentation fault (core dumped)

Looking around goops.scm I can see some classes for applicable structs
that look a bit nicer, but these seem
to use set-object-procedure! which isn't exported (and I can't find a

scheme@(guile-user)> (use-modules (oop goops))
scheme@(guile-user)> (define-class <myclass> (<applicable-struct>))
scheme@(guile-user)> (make <myclass> #:procedure (lambda()(display
"some code")(nelwine)))
<stdin>:5:58: warning: possibly unbound variable `nelwine'
Throw to key `unbound-variable':
ERROR: In procedure module-lookup:
ERROR: Unbound variable: set-object-procedure!

I tried using a generic instead but it didn't make much difference.

What am I doing wrong?

Tristan Colgate-McFarlane
  "You can get all your daily vitamins from 52 pints of guiness, and a
glass of milk"

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