/*
 *  call-seq:
 *     bv.next_unset -> bit_num
 *  
 *  Returns the next unset bit in the bit vector scanning from low order to
 *  high order. This method should only be called on bit vectors which have
 *  been flipped (negated). You should call +#reset_scan+ before
 *  calling this method if you want to scan from the beginning. It is
 *  automatically reset when you first create the bit vector.
 */
VALUE
frt_bv_next_unset(VALUE self)
{
    BitVector *bv;
    GET_BV(bv, self);
    return INT2FIX(bv_scan_next_unset(bv));
}