[boost] [fusion] BOOST_FUSION_ADAPT_TPL_STRUCT

Hello all, I'm trying to do something like this with fusion: struct exists_tag {}; template <typename A> struct unary { type_a m_name; }; template <> struct unary { type_b m_name; }; BOOST_FUSION_ADAPT_TPL_STRUCT((A), (unary)(A), (type_a)(m_name)); BOOST_FUSION_ADAPT_TPL_STRUCT((), (unary)(exists_tag), (type_b)(m_name)); I'm not sure if I'm way off here, or if there is some way to accomplish this that I'm just not seeing. Here's the error that I get when I try to compile this code: ./include/query_tree.h:122:1: error: template parameters not used in partial specialization: ./include/query_tree.h:122:1: error: ‘Oper’ Repeated 8 times. Any ideas? Thanks, Greg