subtract()

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

virtual

Implements Ring.

Definition at line 491 of file frac.cpp.

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

References frac_elem::denom, FRAC_RINGELEM, FRAC_VAL, make_elem(), frac_elem::numer, R_, result(), and set_non_unit_frac().

Referenced by is_equal().