Stan Lippman talked about this here. I thought it was interesting. Summary: Stroustrup originally used class to specify types in templates to avoid introducing a new keyword. Some in the committee worried that this overloading of the keyword led to confusion. Later, the committee introduced a new keyword typename to resolve syntactic ambiguity, and decided … Read more
The problem you describe can be solved by defining the template in the header, or via the approach you describe above. I recommend reading the following points from the C++ FAQ Lite: Why can’t I separate the definition of my templates class from its declaration and put it inside a .cpp file? How can I … Read more
typename and class are interchangeable in the basic case of specifying a template: template<class T> class Foo { }; and template<typename T> class Foo { }; are equivalent. Having said that, there are specific cases where there is a difference between typename and class. The first one is in the case of dependent types. typename … Read more
(See here also for my C++11 answer) In order to parse a C++ program, the compiler needs to know whether certain names are types or not. The following example demonstrates that: t * f; How should this be parsed? For many languages a compiler doesn’t need to know the meaning of a name in order … Read more
Caveat: It is not necessary to put the implementation in the header file, see the alternative solution at the end of this answer. Anyway, the reason your code is failing is that, when instantiating a template, the compiler creates a new class with the given template argument. For example: template<typename T> struct Foo { T … Read more