vec_interchange_rows()

template<typename CoeffRing>

void SMat< CoeffRing >::vec_interchange_rows ( sparsevec *& v, size_t r1, size_t r2 ) const

private

Definition at line 383 of file smat.hpp.

{
  sparsevec *p;
  if (i == j) return;
  if (v == 0) return;
  if (i < j)
    {
      size_t tmp = i;
      i = j;
      j = tmp;
    }
  // So now i > j.
  sparsevec head;
  head.next = v;
  sparsevec *vec1;
  sparsevec *vec2;
  for (p = &head; p->next != 0; p = p->next)
    if (p->next->row <= i) break;
  vec1 = p;
  for (; p->next != 0; p = p->next)
    if (p->next->row <= j) break;
  vec2 = p;
  if (vec1->next != 0 && vec1->next->row == i)
    {
      if (vec2->next != 0 && vec2->next->row == j)
        {
          std::swap(vec1->next->coeff, vec2->next->coeff);
          return;
        }
    }
  else if (vec2->next != 0 && vec2->next->row == j)
    {
      sparsevec *tmp = vec1;
      vec1 = vec2;
      vec2 = tmp;
      j = i;  // Used below.
    }
  else
    return;
 
  sparsevec *tmp = vec1->next;
  if (vec2 != tmp)
    {
      vec1->next = tmp->next;
      tmp->next = vec2->next;
      vec2->next = tmp;
    }
  tmp->row = j;
  v = head.next;
}

References SMat< ACoeffRing >::sparsevec::coeff, SMat< ACoeffRing >::sparsevec::next, p, SMat< ACoeffRing >::sparsevec::row, and std::swap().

Referenced by interchange_rows().