double div( const Array& v, // node positions const Array & f // field value at each node )
double div( const Array& v, // node positions const Array & f // field value at each node const Array & wt // weight at each node )
Vector div( const Array& v, // node positions const Array & f // field value at each node )
Vector div( const Array& v, // node positions const Array & f // field value at each node const Array & wt // weight at each node )
Vector grad( const Array& v, // node positions const Array & f // field value at each node )
Vector grad( const Array& v, // node positions const Array & f // field value at each node const Array & wt // weight at each node )
Matrix grad( const Array& v, // node positions const Array & f // field value at each node )
Matrix grad( const Array& v, // node positions const Array & f, // field value at each node const Array & wt // weight at each node )