Re: Recursion in foreign-safe-lambda

Hi Felix,

Thank you, I see your point. I eventually have the following code that
allows me to recur in C calling callback functions provided by Scheme code.

For the sake of clarity, I have the following Scheme definitions:

>
> (define (simdjson-load filename)
> (let1 (P (foreign-safe-lambda scheme-object "chicken_simdjson_load"
> (const c-string)
> scheme-object
> scheme-object
> scheme-object
> scheme-object
> scheme-object
> scheme-object))
> (P filename list identity make-vector cons (λ (v i x) (vector-set! v i x)
> v) reverse)))
>
> (define (simdjson-load/ondemand filename)
> (let1 (P (foreign-safe-lambda scheme-object
> "chicken_simdjson_load_ondemand"
> (const c-string)
> scheme-object
> scheme-object
> scheme-object
> scheme-object
> scheme-object
> scheme-object))
> (P filename list identity make-vector cons (λ (v i x) (vector-set! v i x)
> v) reverse)))
>

 and in C do the required allocations, passing them as arguments to the
given functions, as in the following C code chunk:

...
> switch (element.type())
> {
> case dom::element_type::ARRAY:
> {
> dom::array array = dom::array(element);
> size_t length = array.size();
>
> C_save(C_fix(length));
> res = C_callback(callback_vector, 1);
>
> size_t i = 0;
> for (dom::element child : array)
> {
>
> tmp = chicken_simdjson_visit(
> child,
> callback_object,
> callback_identity,
> callback_vector,
> callback_list,
> callback_vector_set,
> callback_list_finalize);
>
> C_save(tmp);
> C_save(C_fix(i));
> C_save(res);
>
> res = C_callback(callback_vector_set, 3);
>
> i++;
> }
>
> break;
> }
>


By the way, my aim is to implement a binding over the simdjson
<https://github.com/simdjson/simdjson> library. Can this approach work?

Massimo

>
On Wed, Sep 24, 2025 at 4:14 PM Felix Winkelmann <
[email protected]> wrote:

> On Mon Sep 22, 2025 at 9:46 AM CEST, Massimo Nocentini via Chicken-users
> wrote:
> >
> > I have a progress using foreign-primitive for allocating objects.
> >
> > On the contrary, given the following definitions:
> >
> > (defineparse(foreign-primitivescheme-object(((constc-string) filename)
> > (scheme-objectl))
> > "P(C_k, filename, l);"))
> >
> > where function P is defined in a companion cpp file and reads as follows:
> > C_wordc(C_wordC_k, C_wordl)
> > {
> > if(l==C_SCHEME_END_OF_LIST)
> > {
> > C_return(C_SCHEME_END_OF_LIST);
> > }
> > C_wordcdr=c(C_k, C_i_cdr(l));
> > C_word*ptr=C_alloc(C_SIZEOF_PAIR);
> > C_wordres=C_a_pair(&ptr, C_i_car(l), cdr);
> > C_return(res);
> > }
> > externvoidP(C_wordC_k, constchar*filename, C_wordl)
> > {
> > C_kontinue(C_k, c(C_k, l));
> > }
> > My goal here is to just walk through the given list l and allocate fresh
> > pairs for it. When I try:
> > (parse "something.json" '(1 2 3))
> >
> > I still get:
> >
> > [...]
> >
> > What I'm doing wrong?
>
> This can't work, as C_alloc allocates on the stack and C_return
> in the function "c" will pop any created data again. C_return is
> only valid _inside_ the foreign-primitive body.
>
>
> cheers,
> felix
>
>