lift()

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

virtual

Implements Ring.

Definition at line 415 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
 
  // We assume that Rg is one of the coefficient rings of 'this'
 
  Nterm *t = f;
  if (t == nullptr)
    {
      result = Rg->zero();
      return true;
    }
 
  int nvars0 = n_vars();
  if (Rg != K_)
    {
      const PolynomialRing *Rg1 = Rg->cast_to_PolynomialRing();
      if (Rg1 != nullptr)
        nvars0 -= Rg1->n_vars();
      else
        return false;
    }
 
  exponents_t exp = newarray_atomic(int, nvars0);
  lead_logical_exponents(nvars0, f, exp);
  if (!exponents::is_one(nvars0, exp)) return false;
  if (n_logical_terms(nvars0, f) > 1) return false;
  result = lead_logical_coeff(Rg, f);
  return true;
}

References Ring::cast_to_PolynomialRing(), ExponentVector< int, true >::is_one(), PolynomialRing::K_, lead_logical_coeff(), lead_logical_exponents(), n_logical_terms(), PolynomialRing::n_vars(), newarray_atomic, PolynomialRing::PolynomialRing(), result(), Ring::Ring(), and Ring::zero().