Function id_Compactify

libpolys/polys/simpleideals.cc:1396–1417

2 *skips all zeroes and double elements, searches also for units */

*skips all zeroes and double elements, searches also for units
*/
void id_Compactify(ideal id, const ring r)
{
  int i;
  BOOLEAN b=FALSE;

  i = IDELEMS(id)-1;
  while ((! b) && (i>=0))
  {
    b=p_IsUnit(id->m[i],r);
    i--;
  }
  if (b)
  {
    for(i=IDELEMS(id)-1;i>=0;i--) p_Delete(&id->m[i],r);
    id->m[0]=p_One(r);
  }
  else
  {
    id_DelMultiples(id,r);
  }
  idSkipZeroes(id);
}

/// returns the ideals of initial terms
ideal id_Head(ideal h,const ring r)