Re: A little guile query.

Re: A little guile query.

[Neil Jerram]

Noufal Ibrahim wrote:
> Hello everyone, 
>       I have a question regarding calling C functions with REST
>       arguments. 
>       
>       Basically, I have a 2D array made using 
> 
>       (define foo (create-array (make-array 0 10 10))
> 
>       And then I do a
>       
>       (array-set! foo 1 5 5 )
> 
>       Now, to access this element from the scheme side of the program, I
>       can do 
>       (array-ref foo 5 5)
>       And I get a 1
> 
>       What I want to know is how do I frame the C equivalent of this
>       array reference. 
> 
>       The problem is that the function needs to accept a REST argument
>       that contains the indices of the array. How do I do this? 
> 
>       scm_uniform_vector_ref(scm_c_lookup("foo"),SCM_LIST2(SCM_MAKINUM(5),SCM_MAKINUM(5)));
> 
>       errors out saying 
>       ERROR: Wrong number of arguments to uniform-vector-ref
> 
>       
>       Any sample code snippets on how to do this? 
> 
> Thank you. 

Noufal,

I think the problem is actually the first arg.  scm_c_lookup returns a 
variable which holds your array, not the array itself; you need to add 
scm_variable_ref to fix this:

scm_uniform_vector_ref(scm_variable_ref(scm_c_lookup("foo")),
                        SCM_LIST2(SCM_MAKINUM(5),SCM_MAKINUM(5)));

(Guile's uniform array and vector code is rather bad about spotting args 
that are not actually arrays or vectors!)

Regards,
      Neil


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Re: A little guile query.

[nkv]

Neil Jerram <neil@ossau.uklinux.net> writes:


[...]

> Noufal,
>
> I think the problem is actually the first arg.  scm_c_lookup returns a
> variable which holds your array, not the array itself; you need to add
> scm_variable_ref to fix this:
>
> scm_uniform_vector_ref(scm_variable_ref(scm_c_lookup("foo")),
>                         SCM_LIST2(SCM_MAKINUM(5),SCM_MAKINUM(5)));

[...]

Thanks Neil. I got an answer to this earlier and hadn't checked my Yahoo!
mail for a while. 

Thanks for the reply. :)

-- 
Noufal
http://hcoop.net/~nkv


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