I need little help with dynamic_cast

Question

I have a base class Student and a base class Teacher.
I also have a class Demonstrator(students that assist teachers helping other students), that derives from both Student and Teacher.
To differentiate demonstrators from regular students i tried:
Demonstrator *d=dynamic_cast<Demonstrator *>(students[i]);
//students is an array of objects from the class Student

But the compiler sends an error message:
error: cannot dynamic_cast '*(students + ((sizetype)(((long long unsigned int)i) * 8)))' (of type 'class Student*') to type 'class Demonstrator*'

Answer 1

Is your "students" class polymorphic ? ( Means does it have any virtual function ? )

Answer 2

Thanks. I forgot that.