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Tip of the Day
Language: C++
Expertise: Intermediate
Sep 15, 2000



Building the Right Environment to Support AI, Machine Learning and Deep Learning

Accessing a Class-Internal Type

Here's a common error: you define a class-internal type, say an enum or typedef, and then try to use it as the return type of that class's member function:

class A
 enum sizes {small, medium, large};
 sizes default_size() const{ return medium;}

Up until now, all is fine. However, at a later stage you decide to move the body of default_size() outside the class:

sizes A::default_size() const
 return medium;

All of a sudden, the compiler is moaning and bitching at you that 'sizes' is an unknown type. The problem is that outside the scope of class, you must use a qualified name to refer to an internal type, as follows:

A::sizes A::default_size() const
  return medium;

remember that the compiler recognizes the non-qualified names defined within a class only within that class's scope.

Danny Kalev
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