Template default arguments

Question

If I am allowed to do the following:

template 
class Foo{
};

Why am I not allowed to do the following in main?

Answer 1

With C++17, you can indeed.

This feature is called class template argument deduction and add more flexibility to the way you can declare variables of templated types.

So,

template 
class Foo{};

int main() {
    Foo f;
}

is now legal C++ code.