/*
 *  call-seq:
 *     index_reader.doc_freq(field, term) -> integer
 *
 *  Return the number of documents in which the term +term+ appears in the
 *  field +field+.
 */
static VALUE
frt_ir_doc_freq(VALUE self, VALUE rfield, VALUE rterm)
{
    IndexReader *ir = (IndexReader *)DATA_PTR(self);
    return INT2FIX(ir_doc_freq(ir,
                               frt_field(rfield),
                               StringValuePtr(rterm)));
}