    /*
     *  call-seq:
     *     clause.to_s -> string
     *
     *  Return a string representation of this clause. This will not be used by
     *  BooleanQuery#to_s. It is only used by BooleanClause#to_s and will specify
     *  whether the clause is +:must+, +:should+ or +:must_not+.
     */
    static VALUE
    frb_bc_to_s(VALUE self)
    {
        VALUE rstr;
        char *qstr, *ostr = "", *str;
        int len;
        GET_BC();
        qstr = bc->query->to_s(bc->query, NULL);
        switch (bc->occur) {
            case BC_SHOULD:
                ostr = "Should";
                break;
            case BC_MUST:
                ostr = "Must";
                break;
            case BC_MUST_NOT:
                ostr = "Must Not";
                break;
        }
        len = strlen(ostr) + strlen(qstr) + 2;
        str = ALLOC_N(char, len);
        sprintf(str, "%s:%s", ostr, qstr);
        rstr = rb_str_new(str, len);
        free(qstr);
        free(str);
        return rstr;
    }