Officially, what is typename for?

Question

On occasion I\'ve seen some really indecipherable error messages spit out by gcc when using templates... Specifically, I\'ve had problems where seemingly correc

Answer 1

Following is the quote from Josuttis book:

The keyword typename was introduced to specify that the identifier that follows is a type. Consider the following example:

template 
Class MyClass
{
  typename T::SubType * ptr;
  ...
};

Here, typename is used to clarify that SubType is a type of class T. Thus, ptr is a pointer to the type T::SubType. Without typename, SubType would be considered a static member. Thus

T::SubType * ptr

would be a multiplication of value SubType of type T with ptr.