diff_term()

ring_elem PolyRing::diff_term ( const_monomial m, const_monomial n, monomial resultmon, int use_coeff ) const

protected

Definition at line 2036 of file poly.cpp.

{
  int sign = 0;
  if (!M_->divides(m, n)) return K_->from_long(0);
  if (is_skew_ && use_coeff)
    {
      exponents_t EXP1 = ALLOCATE_EXPONENTS(exp_size);
      exponents_t EXP2 = ALLOCATE_EXPONENTS(exp_size);
      exponents_t EXP3 = ALLOCATE_EXPONENTS(exp_size);
      M_->to_expvector(m, EXP1);
      M_->to_expvector(n, EXP2);
      sign = skew_.diff(EXP1, EXP2, EXP3);
      M_->from_expvector(EXP3, resultmon);
    }
  else
    M_->divide(n, m, resultmon);
  ring_elem result = K_->from_long(1);
  if (!use_coeff) return result;
  gc_vector<int> e1(n_vars()), e2(n_vars());
  exponents_t exp1 = e1.data();
  exponents_t exp2 = e2.data();
  M_->to_expvector(m, exp1);
  M_->to_expvector(n, exp2);
 
  if (is_skew_ && sign < 0) K_->negate_to(result);
 
  for (int i = 0; i < n_vars(); i++)
    {
      for (int j = exp1[i] - 1; j >= 0; j--)
        {
          ring_elem g = K_->from_long(exp2[i] - j);
          K_->mult_to(result, g);
          if (K_->is_zero(result)) return result;
        }
    }
  return result;
}

References ALLOCATE_EXPONENTS, PolynomialRing::exp_size, PolynomialRing::is_skew_, PolynomialRing::K_, PolynomialRing::M_, monomial, PolynomialRing::n_vars(), result(), and PolynomialRing::skew_.

Referenced by diff().