promote()

bool GF::promote ( const Ring * R, const ring_elem f, ring_elem & result ) const

virtual

Implements Ring.

Definition at line 251 of file GF.cpp.

{
  // Rf = Z/p[x]/F(x) ---> GF(p,n)
  // promotion: need to be able to know the value of 'x'.
  // lift: need to compute (primite_element)^e
 
  if (Rf != _originalR) return false;
 
  const Ring *K = _originalR->getCoefficients();
 
  result = from_long(0);
  int exp[1];
  for (Nterm& t : f)
    {
      std::pair<bool, long> b = K->coerceToLongInteger(t.coeff);
      assert(b.first);
      ring_elem coef = from_long(b.second);
      _originalR->getMonoid()->to_expvector(t.monom, exp);
      // exp[0] is the variable we want.  Notice that since the ring is a
      // quotient,
      // this degree is < n (where Q_ = P^n).
      ring_elem g = power(_x_exponent, exp[0]);
      g = mult(g, coef);
      result = ring_elem(internal_add(result.get_int(), g.get_int()));
    }
  return true;
}

References _originalR, _x_exponent, Ring::coerceToLongInteger(), from_long(), ring_elem::get_int(), internal_add(), mult(), power(), result(), and Ring::Ring().