strange template namespace problem - c++

Question

I've got a strange problem with templates and namespaces...
I have the following code which compiles fine..
using namespace boost::multi_index;
template < typename OT, typename KT, KT (OT::* KM)() const, typename KC, typename CMP >
class OrderBook
{
public:
OrderBook() {}
~OrderBook() {}
typedef multi_index_container<
OT,
indexed_by<
ordered_unique<
const_mem_fun< OT, KT, KM >,
KC
>,
ordered_unique<
identity< OT >,
CMP
>
>
> Container;
typedef typename Container::template nth_index< 0 >::type index_0;
typedef typename Container::template nth_index< 1 >::type index_1;
typedef typename index_0::const_iterator const_iterator_0;
typedef typename index_1::const_iterator const_iterator_1;
const_iterator_0 begin0() const { return _container.get<0>().begin(); }
const_iterator_0 end0() const { return _container.get<0>().end(); }
public:
Container _container;
};
However, due to a namespace collision when I insert this code into another project I have to have... (Notice how I've had to remove the using namespace boost::multi_index and manually specify it where needed
template < typename OT, typename KT, KT (OT::* KM)() const, typename KC, typename CMP >
class OrderBook
{
public:
OrderBook() {}
~OrderBook() {}
typedef boost::multi_index::multi_index_container<
OT,
boost::multi_index::indexed_by<
boost::multi_index::ordered_unique<
boost::multi_index::const_mem_fun< OT, KT, KM >,
KC
>,
boost::multi_index::ordered_unique<
boost::multi_index::identity< OT >,
CMP
>
>
> Container;
typedef typename Container::template nth_index< 0 >::type index_0;
typedef typename Container::template nth_index< 1 >::type index_1;
typedef typename index_0::const_iterator const_iterator_0;
typedef typename index_1::const_iterator const_iterator_1;
const_iterator_0 begin0() const { return _container.get<0>().begin(); }
const_iterator_0 end0() const { return _container.get<0>().end(); }
public:
Container _container;
};
Which gives me the following error from g++.
In member function 'typename boost::multi_index::multi_index_container<OT, boost::multi_index::indexed_by<boost::multi_index::ordered_unique<boost::multi_index::const_mem_fun<OT, KT, KM>, KC, mpl_::na>, boost::multi_index::ordered_unique<boost::multi_index::identity<Value>, CMP, mpl_::na>, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, std::allocator<_CharT> >::nth_index<0>::type::const_iterator OrderBook<OT, KT, KM, KC, CMP>::begin0() const':
error: expected primary-expression before ')' token
In member function 'typename boost::multi_index::multi_index_container<OT, boost::multi_index::indexed_by<boost::multi_index::ordered_unique<boost::multi_index::const_mem_fun<OT, KT, KM>, KC, mpl_::na>, boost::multi_index::ordered_unique<boost::multi_index::identity<Value>, CMP, mpl_::na>, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, std::allocator<_CharT> >::nth_index<0>::type::const_iterator OrderBook<OT, KT, KM, KC, CMP>::end0() const':
error: expected primary-expression before ')' token
Sorry for the long error messages, I did consider cleaning them up but I thought I'd better leave them intact in case I removed something crucial.
I tried this...
typedef typename Container::template boost::multi_index::nth_index< 0 >::type index_0;
typedef typename Container::template boost::multi_index::nth_index< 1 >::type index_1;
and it just made g++ even madder :(
Any ideas?

Answer 1

Prefix get<0>() with template:
const_iterator_0 begin0() const { return _container.template get<0>().begin(); }
const_iterator_0 end0 () const { return _container.template get<0>().end(); }
Similar to typename for dependent types, dependent templates have to be prefixed by template:
struct X {
template<class T> void f();
};
template<class T>
void test() {
T::f<int>(); // ill-formed
T::template f<int>(); // ok
}
// ...
test<X>();
And for the curious, that is §14.2/4:
When the name of a member template
specialization appears after . or ->
in a postfix-expression, or after
nested-name-specifier in a
qualified-id, and the
postfix-expression or qualified-id
explicitly depends on a
template-parameter (14.6.2), the
member template name must be prefixed
by the keyword template. Otherwise the
name is assumed to name a
non-template.

Answer 2

Maybe I can guess that some of these functions are not in the boost::multi_index namespace: indexed_b, ordered_unique, const_mem_fun, or identity