Re: Textal interface to Guile

[Rob Browning]

jacques klein <address@hidden> writes:

> I just began to write "a quit (and dirty)" interface between a
> scripting language and Guile, using the gh_eval_str...() functions,
> but I cannot figure out how to "ALWAYS return the result in a C
> string" (like what I get when using guile interactively), or
> otherwise said, is there a function like gh_SCM_to_str() ?  Thank's
> for any hint

Presuming I understand what you want, you could do several things
(note that I haven't tested any of these).  You could define a
function to do the job for you:

  char *
  my_SCM_to_string(SCM obj)
  {
    static SCM scm_to_str = SCM_BOOL_F;

    if(scm_to_str == SCM_BOOL_F) {
      scm_to_str = gh_eval_str("
        (lambda (x)
          (with-output-to-string
            (lambda ()
              (write (x)))))");
      scm_protect_object(scm_to_str);
    }
    return gh_scm2newstr(scm_to_str(obj), NULL);
  }

or you could probably just use scm_simple_format:

  #include <libguile/print.h>

  ...

  my_str = gh_scm2newstr(scm_simple_format(SCM_BOOL_F,
                         gh_str02scm("~S"),
                         gh_list(my_obj, SCM_EOL)));

  ...


  free(my_str);

Note that whether you want write or display in the first example or ~S
or ~A in the second example depends on what you're trying to do.  Also
note that the info docs are a little buggy, and so I'm not sure
whether you're supposed to use SCM_EOL or SCM_UNSPECIFIED, though I
think SCM_EOL is right.  It mentions both in different contexts.

-- 
Rob Browning <address@hidden> PGP=E80E0D04F521A094 532B97F5D64E3930