subtract_in_place_0()

void DPoly::subtract_in_place_0 ( TowerPolynomial & f, const TowerPolynomial g )

private

Definition at line 730 of file dpoly.cpp.

{
  int i;
  if (g == nullptr) return;
  if (f == nullptr)
    {
      f = copy(0, g);
      negate_in_place(0, f);
      return;
    }
  int fdeg = f->deg;
  int gdeg = g->deg;
 
  increase_size_0(g->deg, f);
  for (i = 0; i <= gdeg; i++)
    ZZp_SUBTRACT_TO(charac, f->arr.ints[i], g->arr.ints[i]);
  if (gdeg > fdeg)
    f->deg = gdeg;
  else if (gdeg == fdeg)
    {
      // need to change the degree
      for (int j = fdeg; j >= 0; --j)
        if (f->arr.ints[j] != 0)
          {
            f->deg = j;
            return;
          }
      // at this point, everything is 0!
      dealloc_poly(f);
    }
}

References charac, copy(), dealloc_poly(), increase_size_0(), negate_in_place(), and ZZp_SUBTRACT_TO().

Referenced by subtract_in_place().