index_of_var()

int M2FreeAlgebra::index_of_var ( const ring_elem a ) const

virtual

Reimplemented from Ring.

Definition at line 84 of file M2FreeAlgebra.cpp.

{
  // This function is needed at top level to be able to determine if a ring element is a variable
  //const Poly* f = reinterpret_cast<Poly*>(a.poly_val);
  auto f = reinterpret_cast<const Poly*>(a.get_Poly());
 
  // f is a variable iff: #terms is 1, monomial is [3,1,v], coeff is 1
  if (f->numTerms() != 1) return -1;
  auto i = f->cbegin();
  if (!coefficientRing()->is_equal(coefficientRing()->one(), i.coeff())) return -1;
  return monoid().index_of_variable(i.monom());
}

References coefficientRing(), ring_elem::get_Poly(), FreeMonoid::index_of_variable(), is_equal(), monoid(), and Ring::one().

Referenced by M2FreeAlgebraQuotient::index_of_var().