sub_vector()

vec Ring::sub_vector	(	const vecterm *	v,
		M2_arrayint	r ) const

Definition at line 260 of file ring-vecs.cpp.

{
  if (v == nullptr) return nullptr;
  // Largest component which occurs in v occurs first.
  VECTOR(int) trans(v->comp + 1);
  for (int i = 0; i < v->comp; i++) trans.push_back(-1);
 
  for (unsigned j = 0; j < r->len; j++)
    if (r->array[j] >= 0 && r->array[j] <= v->comp) trans[r->array[j]] = j;
 
  vecterm head;
  vecterm *result = &head;
  for (; v != nullptr; v = v->next)
    if (trans[v->comp] != -1)
      {
        result->next = new_vec();
        result = result->next;
        result->next = nullptr;
        result->coeff = v->coeff;
        result->comp = trans[v->comp];
      }
  result->next = nullptr;
  result = head.next;
 
  vec_sort(result);
  return result;
}

References vec::coeff, vec::comp, new_vec(), vec::next, result(), vec_sort(), and VECTOR.