lift()

bool M2FreeAlgebraQuotient::lift ( const Ring * R, const ring_elem f, ring_elem & result ) const

virtual

Implements Ring.

Definition at line 123 of file M2FreeAlgebraQuotient.cpp.

{
  // R is the target ring
  // f1 is an element of 'this'.
  // set result to be the "lift" of f in the ring R, return true if this is possible.
  // otherwise return false.
 
  // case: R is the coefficient ring of 'this'.
  if (R == coefficientRing())
    {
      auto f = reinterpret_cast<const Poly*>(f1.get_Poly());
      if (f->numTerms() != 1) return false;
      auto i = f->cbegin();
      if (monoid().is_one(i.monom()))
        {
          result = coefficientRing()->copy(i.coeff());
          return true;
        }
      return false;
    }
  if (R == &m2FreeAlgebra())
    {
      // just copy the element into result, considered in the free algebra.
      auto f = reinterpret_cast<const Poly*>(f1.get_Poly());
      auto resultf = new Poly;
      freeAlgebra().copy(*resultf, *f);
      result = ring_elem(reinterpret_cast<void *>(resultf));
      return true;
    }
  
  // at this point, we can't lift it.
  return false;
}

References coefficientRing(), FreeAlgebra::copy(), Ring::copy(), freeAlgebra(), ring_elem::get_Poly(), m2FreeAlgebra(), monoid(), result(), and Ring::Ring().