/*
 *  call-seq:
 *     term_enum.doc_freq -> integer
 *
 *  Returns the document frequency of the current term pointed to by the enum.
 *  That is the number of documents that this term appears in. The method
 *  should only be called after a successful call to TermEnum#next.
 */
static VALUE
frt_te_doc_freq(VALUE self)
{
    TermEnum *te = (TermEnum *)DATA_PTR(self);
    return INT2FIX(te->curr_ti.doc_freq);
}