/*
 *  call-seq:
 *     fis.tokenized_fields -> symbol array
 *
 *  Return a list of the field names (as symbols) of all the tokenized fields
 *  in the index.
 */
static VALUE
frt_fis_get_tk_fields(VALUE self)
{
    FieldInfos *fis = (FieldInfos *)DATA_PTR(self);
    VALUE rfield_names = rb_ary_new();
    int i;
    for (i = 0; i < fis->size; i++) {
        if (!fi_is_tokenized(fis->fields[i])) continue;
        rb_ary_push(rfield_names, ID2SYM(rb_intern(fis->fields[i]->name)));
    }
    return rfield_names;
}