subtract()

ring_elem LocalRing::subtract ( const ring_elem f, const ring_elem g ) const

virtual

Implements Ring.

Definition at line 510 of file localring.cpp.

{
  const local_elem *f = a.get_local_elem();
  const local_elem *g = b.get_local_elem();
  ring_elem top, bottom;
 
  if (mRing->is_equal(f->denom, g->denom))
    {
      top = mRing->subtract(f->numer, g->numer);
      bottom = mRing->copy(f->denom);
    }
  else
    {
      top = mRing->mult(f->numer, g->denom);
      ring_elem tmp = mRing->mult(f->denom, g->numer);
      mRing->subtract_to(top, tmp);
      bottom = mRing->mult(f->denom, g->denom);
      if (mRing->is_zero(bottom)) return set_non_unit_frac(f->denom);
    }
  local_elem *result = make_elem(top, bottom);
  return ring_elem(result);
}

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

Referenced by is_equal().