Why is there "class" in "template <class x>"?

Question

What does the "class" part of a template statement do?

Example:

template <class T>
class Something
{
    public:
        Something(const T &something);
}

And what else can go there? I usually only see "class".

Answer 1

The class keyword means the same thing as the typename keyword for the most part. They both indicates that T is a type.

The only difference between the keywords class and typename is that class can be used to provide class template template arguments to a template, whereas typename can't. Consider:

template<template <class T> class U> // must be "class"
std::string to_string(const U<char>& u)
{
  return std::string(u.begin(),u.end());
}

The only other thing you can put in place of the class or typename keywords is an integral type. For example:

template<std::size_t max>
class Foo{...};
...
Foo<10> f;

For a concrete example of this, take a look at std::bitset<N> in the standard library.