memset(p->a, 0, sizeof(p->a[0])*newSize );
  for(i=0; i<old.sz; i++){
    int e = old.a[i];
    if( e>0 ){
      unsigned h = bag_hash(e)%newSize;
      while( p->a[h] ){
        h++;
        if( (int)h==newSize ) h = 0;
      }
      p->a[h] = e;
      nLive++;
    }else if( e<0 ){
      nDel++;
    }
  }

  if( p->used+1 >= p->sz/2 ){
    int n = p->sz*2;
    bag_resize(p,  n + 20 );
  }
  h = bag_hash(e)%p->sz;
  while( p->a[h]>0 && p->a[h]!=e ){
    h++;
    if( (int)h>=p->sz ) h = 0;
  }
  if( p->a[h]<=0 ){
    if( p->a[h]==0 ) p->used++;
    p->a[h] = e;
    p->cnt++;
    rc = 1;
  }

  assert( e>0 );
  if( p->sz==0 ){
    return 0;
  }
  h = bag_hash(e)%p->sz;
  while( p->a[h] && p->a[h]!=e ){
    h++;
    if( (int)h>=p->sz ) h = 0;
  }
  return p->a[h]==e;
}

/*
** Remove element e from the bag if it exists in the bag.
** If e is not in the bag, this is a no-op.
*/
void bag_remove(Bag *p, int e){
  unsigned h;
  assert( e>0 );
  if( p->sz==0 ) return;
  h = bag_hash(e)%p->sz;
  while( p->a[h] && p->a[h]!=e ){
    h++;
    if( (int)h>=p->sz ) h = 0;
  }
  if( p->a[h] ){
    int nx = h+1;
    if( nx>=p->sz ) nx = 0;
    if( p->a[nx]==0 ){
      p->a[h] = 0;
      p->used--;

int bag_next(Bag *p, int e){
  unsigned h;
  assert( p->sz>0 );
  assert( e>0 );
  h = bag_hash(e)%p->sz;
  while( p->a[h] && p->a[h]!=e ){
    h++;
    if( (int)h>=p->sz ) h = 0;
  }
  assert( p->a[h] );
  h++;
  while( (int)h<p->sz && p->a[h]<=0 ){
    h++;
  }
  return (int)h<p->sz ? p->a[h] : 0;
}

/*
** Return the number of elements in the bag.
*/
int bag_count(Bag *p){
  return p->cnt;
}