Defining Member Functions Outside the Class Definition; Class Scope
Even though a member function declared in a class definition may be defined outside that class definition (and “tied” to the class via the scope resolution operator), that member function is still within that class’s scope—that is, its name is known to other class members referred to via an object of the class, a reference to an object of the class, a pointer to an object of the class or the scope resolution operator. We’ll say more about class scope shortly.
If a member function is defined in a class’s body, the member function is implicitly declared inline. Remember that the compiler reserves the right not to inline any function.
Performance Tip 9.1
Defining a member function ...