/*
 *  call-seq:
 *     index_reader.term_vector(doc_id, field) -> TermVector
 *
 *  Return the TermVector for the field +field+ in the document at +doc_id+ in
 *  the index. Return nil of no such term_vector exists. See TermVector.
 */
static VALUE
frt_ir_term_vector(VALUE self, VALUE rdoc_id, VALUE rfield)
{
    IndexReader *ir = (IndexReader *)DATA_PTR(self);
    TermVector *tv;
    VALUE rtv;
    tv = ir->term_vector(ir, FIX2INT(rdoc_id), frt_field(rfield));
    if (tv) {
        rtv = frt_get_tv(tv);
        tv_destroy(tv);
        return rtv;
    }
    else {
        return Qnil;
    }
}