extract_divisible_by_x()

Nterm * extract_divisible_by_x	(	Nterm *&	ff,
		int	i )

Definition at line 191 of file NAG.cpp.

{
  /* Extracts into fx the terms divisible by the (n-1-i)-th variable "x"
     and divides them by x. (exponent vectors are assumed to be reversed)
     Note: terms in fx may not be in monomial order. */
  Nterm* fx = nullptr;
  Nterm* f = ff;
  Nterm* prev_f = nullptr;
  while (f != nullptr)
    {
      if (f->monom[i] == 0)
        {
          prev_f = f;
          f = f->next;
        }
      else
        {
          f->monom[i]--;  // divide by x
          if (prev_f != nullptr)
            {
              prev_f->next = f->next;  // extract
            }
          else
            {
              ff = f->next;  // ... or cut
            }
          f->next = fx;  // prepend to fx
          fx = f;
          f = (prev_f == nullptr) ? ff : prev_f->next;
        }
    }
  return fx;
}

References Nterm::monom, and Nterm::next.

Referenced by SLP< Field >::poly_to_horner_slp().