Question

Can’t google this out so just looking for a quick answer. What this syntax means and is it standard C++?

template <class ...Options>
class list_base_hook;

The code is from boost libraries.
http://www.boost.org/doc/libs/1_52_0/doc/html/intrusive/usage.html

Answer 1

In C++11 it’s a variadic template parameter.

Boost uses that syntax for “psuedo-variadic” templates from C++03 too – meaning it is a bunch typenames with defaults. Not exactly the same as C++11’s variadics. Like this:

template <class opt1 = dummy, class op2 = dummy, class op3 = dummy, /* and so on up to a large N */>
class list_base_hook;