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