multinomial() [2/2]

ring_elem WeylAlgebra::multinomial	(	const_exponents	exptop,
		const_exponents	exp ) const

Definition at line 576 of file weylalg.cpp.

{
  ring_elem result = K_->from_long(1);
  for (int i = 0; i < nvars_; i++)
    if (exptop[i] > 0)
      {
        for (int j = exptop[i]; j > exp[i]; j--)
          {
            ring_elem c = K_->from_long(j);
            ring_elem d = K_->from_long(exptop[i] - j + 1);
            K_->mult_to(result, c);
            ring_elem e = K_->divide(result, d);  // exact
            K_->remove(c);
            K_->remove(d);
            K_->remove(result);
            result = e;
          }
      }
  return result;
}

References PolynomialRing::K_, PolynomialRing::nvars_, and result().