imp_attempt_to_cancel_lead_term()

bool PolyRing::imp_attempt_to_cancel_lead_term ( ring_elem & f, ring_elem g, ring_elem & coeff, monomial monom ) const

protected

Definition at line 1010 of file poly.cpp.

{
  bool result;
  Nterm *t = f;
  Nterm *s = g;
  if (t == nullptr || s == nullptr) return true;
  if (K_->is_field())
    {
      coeff = K_->divide(t->coeff, s->coeff);
      result = true;
    }
  else if (K_ == globalZZ)
    {
      ring_elem r = globalZZ->remainderAndQuotient(t->coeff, s->coeff, coeff);
      result =
          (globalZZ->is_zero(r));  // true means lead term will be cancelled.
    }
  else
    {
      throw exc::internal_error("should not get to this code in imp_attempt_to_cancel_lead_term");
      coeff = K_->zero();
      result = false;
      // What do we do here??  Call divide, and hope for the best?
    }
  if (!K_->is_zero(coeff))
    {
      if (is_skew_)
        {
          exponents_t EXP1 = ALLOCATE_EXPONENTS(exp_size);
          exponents_t EXP2 = ALLOCATE_EXPONENTS(exp_size);
          exponents_t EXP3 = ALLOCATE_EXPONENTS(exp_size);
          M_->to_expvector(t->monom, EXP1);
          M_->to_expvector(s->monom, EXP2);
          int sign = skew_.divide(EXP1, EXP2, EXP3);
          M_->from_expvector(EXP3, monom);
          if (sign < 0) K_->negate_to(coeff);
          imp_subtract_multiple_to(f, coeff, monom, g);
        }
      else
        {
          M_->divide(t->monom, s->monom, monom);
          imp_subtract_multiple_to(f, coeff, monom, g);
        }
    }
  return result;
}

References ALLOCATE_EXPONENTS, Nterm::coeff, PolynomialRing::exp_size, globalZZ, imp_subtract_multiple_to(), PolynomialRing::is_skew_, PolynomialRing::K_, PolynomialRing::M_, Nterm::monom, monomial, result(), s, and PolynomialRing::skew_.

Referenced by division_algorithm(), division_algorithm(), and powerseries_division_algorithm().