getSmallIntegerCoefficients() [2/2]

bool RingElement::getSmallIntegerCoefficients

(

std::vector< long > &

result_coeffs

)

const

Definition at line 421 of file relem.cpp.

{
  const PolynomialRing *R = get_ring()->cast_to_PolynomialRing();
  const Ring *K = R->getCoefficientRing();
  if (R == nullptr || R->n_vars() != 1)
    {
      throw exc::engine_error(
          "Expected a polynomial in a univariate polynomial ring");
      return false;  // Should not be needed
    }
 
  if (is_zero())
    {
      result_coeffs.resize(0);
      return true;
    }
  int lo, deg;  // ignore lo, and deg == degree of the univariate polynomial f.
  R->degree_of_var(0, get_value(), lo, deg);
  result_coeffs.resize(deg + 1);
  for (int i = 0; i <= deg; i++) result_coeffs[i] = 0;
  int exp[1];
  for (Nterm& t : get_value())
    {
      std::pair<bool, long> res = K->coerceToLongInteger(t.coeff);
      if (not res.first)
        {
          // At this point, the answer is meaningless
          result_coeffs.resize(0);
          return false;
        }
      long coeff = res.second;
 
      R->getMonoid()->to_expvector(t.monom, exp);
      assert(exp[0] >= 0);
      assert(exp[0] <= deg);
      result_coeffs[exp[0]] = coeff;
    }
  return true;
}

References Ring::cast_to_PolynomialRing(), Ring::coerceToLongInteger(), get_ring(), get_value(), is_zero(), and R.

Referenced by M2::ARingGFFlint::ARingGFFlint(), M2::ARingGFFlintBig::ARingGFFlintBig(), getGFRepresentation(), M2::ARingGFFlint::promote(), M2::ARingGFFlintBig::promote(), and M2::ARingGFM2::promote().