promote()

bool PolyRing::promote ( const Ring * R, const ring_elem f, ring_elem & result ) const

virtual

Implements Ring.

Definition at line 379 of file poly.cpp.

{
  // case 1:  Rf = A[x]/J ---> A[x]/I  is one of the 'base_ring's of 'this'.
  // case 2:  Rf = A      ---> A[x]/I  is the ring of scalars
 
  // Cases:
  //  Rf is a poly ring (or quotient of one), with the same coeff ring as this.
  //  Rf is a poly ring (or quotient) with the same monoid as this (but coeffs
  //  are maybe different).
  //  Rf is the coeff ring of this
  //  Rf is not the coeff ring K of this, but is a base ring of K (e.g. ZZ -->
  //  QQ, A --> frac(A), any others?)
  //  Rf is a poly ring in a smaller number of variables
 
  int nvars0 = n_vars();
  if (Rf != K_)
    {
      const PolynomialRing *Rf1 = Rf->cast_to_PolynomialRing();
      if (Rf1 != nullptr)
        nvars0 -= Rf1->n_vars();
      else
        return false;
      if (Rf1 && nvars0 == 0)
        {
          result = copy(f);
          return true;
        }
    }
 
  exponents_t exp = newarray_atomic_clear(int, nvars0);
  result = make_logical_term(Rf, f, exp);
  return true;
}

References Ring::cast_to_PolynomialRing(), copy(), PolynomialRing::K_, make_logical_term(), PolynomialRing::n_vars(), newarray_atomic_clear, PolynomialRing::PolynomialRing(), result(), and Ring::Ring().