Trouble creating SRFI-9 Record in C
Good day guile-users,
I am having a struggle with SRFI-9 records. They look very
convenient, so i'd like to use them in my Guile scripts. However,
i'm not sure how to correctly construct them from C-land. I have
something like the following:
```
(define-record-type
(make-foo a b)
foo?
(a foo-a)
(b foo-b))
```
In Guile land, that works great. Now, i want to create a foo in C
and pass it to a function in the Guile script. I do something
like the following:
```
scm_c_primitive_load("foo.scm");
scm_call_5(scm_variable_ref(scm_c_lookup("make-foo")),
scm_from_utf8_string("blah"),
scm_from_int32(Int32(42)))
```
However, this results in an error:
guile: uncaught exception:
Wrong type to apply: #
I've tried with and without (define-module foo) at the top of the
file, that doesn't seem to make a difference. I've been able to
work around the issue by defining a wrapper (define (foo-prime a
b) (make-foo a b)) and using that in C as shown above, but that
feels ugly. I'm probably missing something obvious, but trawling
the mailing list didn't turn up anything i could understand.
Does anyone see what i'm doing wrong, or can i simply not use
SRFI-9 records in this way?
Thanks, 🙌
p.
Re: Trouble creating SRFI-9 Record in C
On Sat, 11 Sep 2021, paul wrote:
> In Guile land, that works great. Now, i want to create a foo in C
> and pass it to a function in the Guile script. I do something
> like the following:
>
> ```
> scm_c_primitive_load("foo.scm");
> scm_call_5(scm_variable_ref(scm_c_lookup("make-foo")),
>scm_from_utf8_string("blah"),
>scm_from_int32(Int32(42)))
> ```
>
> However, this results in an error:
>
> guile: uncaught exception:
> Wrong type to apply: #
Seems like `make-foo` is a syntax-transformer and not a procedure. You
can not call a syntax-transformer. I don't think you can do much with a
syntax-transformer in C.
>
> I've tried with and without (define-module foo) at the top of the
> file, that doesn't seem to make a difference. I've been able to
> work around the issue by defining a wrapper (define (foo-prime a
> b) (make-foo a b)) and using that in C as shown above, but that
> feels ugly. I'm probably missing something obvious, but trawling
> the mailing list didn't turn up anything i could understand.
By making a wrapper, you're effectively creating a procedure that can
use the `make-foo` syntax because it's in Scheme and it's solved a
expansion time.
--
Olivier Dion
Polymtl
