lift()

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

virtual

Implements Ring.

Definition at line 267 of file localring.cpp.

{
  // Rg = R ---> frac R
  // f is an element of frac R.
 
  ring_elem
      hdenom;  // used in the case when the denominator can be a unit, but not 1
               // e.g. when this = frac (QQ[x,y,z]).  Is an element of
  if (Rg == mRing)
    {
      const local_elem *h = f.get_local_elem();
      if (mRing->is_equal(h->denom, mRing->one()))
        {
          result = mRing->copy(h->numer);
          return true;
        }
      else
        {
          if (mRing->is_field())
            {
              // XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
              // try to lift denominator.  If can, can lift, otherwise not.
              if (mRing->lift(mRing, h->denom, hdenom))
                {
                  ring_elem hinv = mRing->invert(hdenom);
                  result = mRing->mult(hinv, h->numer);
                  return true;
                }
            }
        }
    }
  return false;
}

References local_elem::denom, ring_elem::get_local_elem(), mRing, local_elem::numer, result(), and Ring::Ring().