+/** Inert partial differentiation operator. */
+DECLARE_FUNCTION_2P(Derivative)
+
+ex lsolve(const ex &eqns, const ex &symbols);
+
+/** Symmetrize expression over a set of objects (symbols, indices). */
+ex symmetrize(const ex & e, exvector::const_iterator first, exvector::const_iterator last);
+
+/** Symmetrize expression over a set of objects (symbols, indices). */
+inline ex symmetrize(const ex & e, const exvector & v)
+{
+ return symmetrize(e, v.begin(), v.end());
+}
+
+/** Antisymmetrize expression over a set of objects (symbols, indices). */
+ex antisymmetrize(const ex & e, exvector::const_iterator first, exvector::const_iterator last);