On 01/16/2005 03:11 PM, Larry Evans wrote:
On 01/15/2005 05:26 PM, David Abrahams wrote: [snip]
Finally, the kind of access being done is completely different from what's done with tuple.
I've not looked *real* close at tuple, but I assumed boost::tuple had the following type of access: [snip] Could you elaborate on how the kinds of element access in boost::tuple and that of tuple_type in get_ith_head_test.cpp are different?
Maybe you meant the way element access was being done. I've just looked at boost/tuple/detail/tuple_basic.hpp. I see two templates which may be candidates for how tuple implements get. The first is: template< int N > struct get_class { template<class RET, class HT, class TT > inline static RET get(const cons<HT, TT>& t) { #if BOOST_WORKAROUND(__IBMCPP__,==600) // vacpp 6.0 is not very consistent regarding the member template keyword // Here it generates an error when the template keyword is used. return get_class<N-1>::get<RET>(t.tail); #else return get_class<N-1>::BOOST_NESTED_TEMPLATE get<RET>(t.tail); #endif } ... and the 2nd, which looks closer to what could be the implementation is prefixed with comment: // -cons type accessors ---------------------------------------- // typename tuples::element<N,T>::type gets the type of the // Nth element ot T, first element is at index 0 // ------------------------------------------------------- but the code for that looks very similar to get_ith_tail. The difference is that get_ith_tail uses specialization to split apart the Head and Tail parts and recurses on the Tail, whereas tuples:element uses the nested typedef for tail_type to recurse on the tail. Do you mean this is completely different, or is there some other code I should look at to see how tuple accesses its elements?