Trouble creating SRFI-9 Record in C

Trouble creating SRFI-9 Record in C

[paul]

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 <foo>
  (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: #<syntax-transformer make-foo>

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

[Olivier Dion via General Guile related discussions]

On Sat, 11 Sep 2021, paul <paul@inktvis.org> 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: #<syntax-transformer make-foo>

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

Re: Trouble creating SRFI-9 Record in C

[Matt Wette]

maybe add

(define (make-foo-x a b) (make-foo a b))

then call make-foo-x (or reverse names)

On 9/10/21 7:27 PM, paul wrote:
> 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 <foo>
>  (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: #<syntax-transformer make-foo>
>
> 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

[paul]

Hey Matt,

Yeah that was exactly my workaround 🙂 I was wondering whether i could use the syntax transformer more "directly" from C, or something like that. 

Thanks,
paul

> On 11 Sep 2021, at 23:31, Matt Wette <matt.wette@gmail.com> wrote:
> 
> maybe add
> 
> (define (make-foo-x a b) (make-foo a b))
> 
> then call make-foo-x (or reverse names)
> 
>> On 9/10/21 7:27 PM, paul wrote:
>> 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 <foo>
>>  (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: #<syntax-transformer make-foo>
>> 
>> 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.
>> 
> 
>