[Boost-users] [Boost.MultiIndex] Parameterizing multi_index_container on a template parameter

From: Julius Ziegler (ziegler_at_[hidden])
Date: 2008-07-04 12:16:09

Hello,

I am having problems using a multi_index_container in the context of a 
template class, and I am hoping someone here can help me. This is a 
condensed example:

template<class T> struct C {
   typedef multi_index_container<T> SomeSet;
   SomeSet container;

   // I learned I need typename, since this is an implicit type
   typedef typename multi_index_container<T>::nth_index<0>::type 
SomeSetIndex;

   void f()
   {
     SomeSetIndex& index = container.get<0>();
   }
};

The typedef for SomeSetIndex did not compile. g++-4.2 reported (I 
stripped something from the message that I think is not relevant):

error: non-template 'nth_index' used as template
note: use 'multi_index_container<T, [stripped] >::template nth_index' to 
indicate that it is a template

Now I (blindly) tried this declaration:

typedef typename multi_index_container<T>::template nth_index<0>::type

g++ gets past it, but now reports a syntax error in function f, when 
index gets initialised.

Can someone please explain that first error message to me? Any help is 
appreciated.

-J