Variadic templates

Question

I have seen a lot of links introducing the variadic templates. But I have never seen any compilable example that demonstrates this approach.

Could someone provide me

Answer 1

This is an example of variadic templates that I put up on my blog: http://thenewcpp.wordpress.com/2011/11/23/variadic-templates-part-1-2/

It compiles. It demonstrates finding the largest type from a group of types.

#include <type_traits>

template <typename... Args>
struct find_biggest;

//the biggest of one thing is that one thing
template <typename First>
struct find_biggest<First>
{
  typedef First type;
};

//the biggest of everything in Args and First
template <typename First, typename... Args>
struct find_biggest<First, Args...>
{
  typedef typename find_biggest<Args...>::type next;
  typedef typename std::conditional
  <
    sizeof(First) >= sizeof(next),
    First,
    next
  >::type type;
};

Answer 2

another syntax: expanding, e.g.

template<typename VAL, typename... KEYS>
class MyMaps
{
  typedef std::tuple< std::map<KEYS,VAL>... > Maps;
}

hence:

MyMaps<int,int,string>:Maps

is now actually:

std::tuple<std::map<int,int>,std::map<string,int> >