Does the typename keyword exist in C++, for backwards compatibility with “C templates?”

Question

I’m taking a C++ class, and my teacher mentioned in passing that the typename keyword existed in C++ (as opposed to using the class keyword in a template declaration), for backwards compatibility with “C templates.”

This blew my mind. I’ve never seen or heard tell of anything like C++’s templates (except, perhaps, the preprocessor… and that’s not really the same thing at all) in ANSI C. So, did I miss something huge somewhere, or is this a really esoteric extension by gcc or something, or is my teacher way off-base?

Answer 1

I think your teacher is off base.

See Stan Lippman's post: Why C++ Supports both Class and Typename for Type Parameters for the real reason why C++ supports both.

Answer 2

Perhaps the phrase your teacher was aiming for was along the lines of "...for backwards compatibility with C types", i.e., recognizing the problem that template<class T> is misleading when T is a C-style built-in type such as char or int, as others have said. But that's not a class! :-)

A while back a few GCC folks were suggesting that making the template machinery available to the C compiler would be a good way to implement C99's <tgmath.h>, but that doesn't appear to have come to anything.