index_of_var()

int PolyRing::index_of_var ( const ring_elem a ) const

virtual

Implements PolynomialRing.

Definition at line 319 of file poly.cpp.

{
  Nterm *f = a;
  if (f == nullptr || f->next != nullptr) return -1;
  if (!K_->is_equal(f->coeff, K_->from_long(1))) return -1;
  int result = -1;
  exponents_t EXP1 = ALLOCATE_EXPONENTS(exp_size);
  M_->to_expvector(f->monom, EXP1);
  for (int i = 0; i < n_vars(); i++)
    if (EXP1[i] > 1)
      return -1;
    else if (EXP1[i] == 1)
      {
        if (result >= 0) return -1;
        result = i;
      }
  return result;
}

References ALLOCATE_EXPONENTS, Nterm::coeff, PolynomialRing::exp_size, PolynomialRing::K_, PolynomialRing::M_, Nterm::monom, PolynomialRing::n_vars(), Nterm::next, and result().