doc/snippets/MatrixBase_template_int_start.cpp

RowVector4i v = RowVector4i::random();
cout << "Here is the vector v:" << endl << v << endl;
cout << "Here is v.start(2):" << endl << v.start<2>() << endl;
v.start<2>().setZero();
cout << "Now the vector v is:" << endl << v << endl;