Re: using guile like a awk filter in a C program.

[Simon Tournier]

Hi,

On Fri, 10 May 2024 at 15:55, Pierre LINDENBAUM 
<Pierre.Lindenbaum@univ-nantes.fr> wrote:

>       ```
>       header = read_header(input);
>       guile_context = my_initialize_guile(header, argc_argv_user_script)
>       variant = new_variant();
>       while(read_variant(input,header,variant)) {
>               if(!my_guile_test(guile_context,header,variant)) {
>                       continue;
>                       }
>               do_something(header,variant)
>               }
>       dispose_variant(variant)
>       my_dispose_guile(guile_context)
>       dispose_header(header)
>       ```
>
> and would may be be invoked like:
>
> ```
> ./a.out -e '(and (variant-is-snp? ) (equals? (variant-allele-count) 2))' 
> input.vcf > output.vcf
> ```

[...]


> - is it possible to use guile for such task ? More precisely, can I 
> compile the guile script just once in `my_initialize_guile` and use it 
> in the while loop without having to recompile it.

I am not sure to well understand.  Since, it could be read two ways:

 + Call Scheme from C
 + Call C from Scheme

Will the main loop be in C-like or in Guile?


> - furthermore, what's the best practice to include the user's script in 
> a larger script that would include the definitions of `variant-is-snp?` 
> , `variant-allele-count`, etc...

Maybe modules?

> - is there any implementation that works like this (something like a AWK 
> script in guile) ?

What you want to replace is the driver – currently implemented in AWK.
You would like to have the driver (glue code) in Guile.  Is it correct?

> - is there any way to make the program stateless ? I mean, any 
> invocation of `my_guile_test` would erase the definition of the previous 
> variant

Well, this question depends on the above, I guess. :-)

Cheers,
simon