rawConvolve()

engine_RawRingElementArrayOrNull rawConvolve	(	engine_RawRingElementArray	H,
		int	convolve_type )

Definition at line 762 of file ringelement.cpp.

{
  // convolve_type == 1: E_n = E_(n-1) * H_1 - E(n-2) * H_2 + ... + (-1)^n * H_n
  // convolve_type == 2: n * E_n = E_(n-1) * H_1 - E(n-2) * H_2 + ... + (-1)^n *
  // H_n
  // others of interest?  These are good for translating between symmetric
  // functions of type E,H,P
 
  // H_0 is ignored... (OR: should we instead shift everything: first entry of H
  // is denoted H_1...?)
 
  try
    {
      int len = H->len;
      if (len <= 1)
        {
          ERROR("expected ring element array of length at least 2");
          return nullptr;
        }
      const PolyRing *P = H->array[1]->get_ring()->cast_to_PolyRing();
      if (P == nullptr)
        {
          ERROR("expected a polynomial ring");
          return nullptr;
        }
      VECTOR(ring_elem) input_relems(len);
      VECTOR(ring_elem) output_relems(len);
      for (int i = 0; i < len; i++) input_relems[i] = H->array[i]->get_value();
      convolve(P, input_relems, output_relems, convolve_type);
 
      engine_RawRingElementArray result =
          getmemarraytype(engine_RawRingElementArray, len);
      result->len = len;
      for (int i = 0; i < result->len; i++)
        result->array[i] = RingElement::make_raw(P, output_relems[i]);
 
      return result;
  } catch (const exc::engine_error& e)
    {
      ERROR(e.what());
      return nullptr;
  }
}

References convolve(), ERROR, getmemarraytype, RingElement::make_raw(), result(), and VECTOR.