rawExtendedGCDRingElement()

const RingElement * rawExtendedGCDRingElement	(	const RingElement *	f,
		const RingElement *	g,
		const RingElement **	A,
		const RingElement **	B )

Definition at line 553 of file factory.cpp.

{
  const bool inExtension = false;
  const RingElement *ret;
  const PolynomialRing *P = f->get_ring()->cast_to_PolynomialRing();
  const PolynomialRing *P2 = g->get_ring()->cast_to_PolynomialRing();
  *A = nullptr;
  *B = nullptr;
  if (P == nullptr)
    {
      if (f->get_ring()->cast_to_Tower() != nullptr)
        return towerExtendedGCD(f, g, A, B);
      // else we really do have an error:
      ERROR("expected polynomial ring");
      return nullptr;
    }
  if (P != P2)
    {
      ERROR("encountered different rings");
      return nullptr;
    }
 
  if (f->is_zero())
    {
      *A = RingElement::make_raw(P, P->zero());
      *B = RingElement::make_raw(P, P->one());
      return g;
    }
 
  if (g->is_zero())
    {
      *A = RingElement::make_raw(P, P->one());
      *B = RingElement::make_raw(P, P->zero());
      return f;
    }
 
  struct enter_factory foo(P);
  if (foo.mode == modeError) return nullptr;
  if (foo.mode == modeGF)
    {
      set_GF_minimal_poly(P);
    }
  CanonicalForm p = convertToFactory(*f, inExtension);
  CanonicalForm q = convertToFactory(*g, inExtension);
  CanonicalForm a, b;
  CanonicalForm h = extgcd(p, q, a, b);
  ret = convertToM2(P, h);
  if (error())
    {
      algebraicElement_M2 = nullptr;
      return nullptr;
    }
  *A = convertToM2(P, a);
  if (error())
    {
      algebraicElement_M2 = nullptr;
      return nullptr;
    }
  *B = convertToM2(P, b);
  if (error())
    {
      algebraicElement_M2 = nullptr;
      return nullptr;
    }
  algebraicElement_M2 = nullptr;
  return ret;
}

References algebraicElement_M2, Ring::cast_to_PolynomialRing(), Ring::cast_to_Tower(), convertToFactory(), convertToM2(), ERROR, error(), RingElement::get_ring(), RingElement::is_zero(), RingElement::make_raw(), enter_factory::mode, modeError, modeGF, Ring::one(), p, towerExtendedGCD(), and Ring::zero().

Referenced by PolyRingQuotient::invert().