Does anyone have an applicable struct example

Does anyone have an applicable struct example

[Tristan Colgate]

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
definition)....

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"

Re: Does anyone have an applicable struct example

[Tristan Colgate]

I've had a further play and read around the source, and got things
working via goops atleast (still not sure how to use the applicable
structs directly).

The following code works....

(define-class <myclass> (<applicable-struct>) (a))
(make <myclass>)
(slot-set! $1 'procedure (lambda()(...)))
($1)
(slot-set! $1 'a 1)
etc...

This plays nice with write and display method overrides too (which is
what I was after).


On 25 June 2010 10:14, Tristan Colgate <tcolgate@gmail.com> wrote:
> 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
> definition)....
>
> 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"
>



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

Re: Does anyone have an applicable struct example

[Nala Ginrut]

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2010/6/25 Tristan Colgate <tcolgate@gmail.com>

> 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?
>
>
NOT "nelwine" IT IS "newline"

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Re: Does anyone have an applicable struct example

[Andy Wingo]

Hi Tristan,

On Fri 25 Jun 2010 11:14, Tristan Colgate <tcolgate@gmail.com> writes:

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

Apologies for the lack of docs; it's on my list, but I haven't gotten to
it yet.

> 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)

Ew, will fix.

> 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
> definition)....

I have applied your fix to this one.

> What am I doing wrong?

You are doing everything right, it's just that you found a couple bugs
in a recently-rewritten part of Guile. Apologies again!

Happy hacking,

Andy
-- 
http://wingolog.org/

Re: Does anyone have an applicable struct example

[Andy Wingo]

Hi Tristan,

On Fri 25 Jun 2010 02:14, Tristan Colgate <tcolgate@gmail.com> writes:

> 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)

Thanks for the report. I have fixed Guile so that it now does this:

  scheme@(guile-user)> (define <mything-vtable> (make-struct <applicable-struct-vtable> 0))
  scheme@(guile-user)> (make-struct <mything-vtable> 0)
  <unnamed port>:2:1: In procedure struct-vtable?:
  <unnamed port>:2:1: vtable has invalid layout: #f

Indeed you didn't specify a layout when making <mything-vtable>. Try
this:

  scheme@(guile-user)> (define <mything-vtable> (make-struct <applicable-struct-vtable> 0 'pw))
  scheme@(guile-user)> (make-struct <mything-vtable> 0)
  $1 = #<struct:23ce1e0 pw 24a8ec0>
  scheme@(guile-user)> (make-struct <mything-vtable> 0 (lambda () 10))
  $2 = #<struct:23ce1e0 pw 24b7920 proc: #<procedure 24b7940 at <current input>:4:32 ()>>
  scheme@(guile-user)> ($2)
  $3 = 10

You see, 'pw is the "minimum layout" for an applicable struct:

  scheme@(guile-user)> (define <mything-vtable> (make-struct <applicable-struct-vtable> 0 'pr))
  <unnamed port>:1:26: In procedure %inherit-vtable-magic:
  <unnamed port>:1:26: invalid applicable struct layout

To add fields you add them after the 'pw. Like 'pwpwpw, for two user
fields.

This whole thing is very low-level though, and needs proper
documentation. It would be nice to clean up the "layout" to not be a
symbol, but that's a job...

Andy
-- 
http://wingolog.org/