subscript operator in boost::lambda supports only the following types (from lambda/detail/operator_return_type_traits.hpp
of my install of boost 1.53):
A*
, A[N]
, std::map
, std::multimap
, std::deque
, std::vector
, std::basic_string
. Everything else becomes detail::unspecified
, which you see in your compiler diagnostic.
To make boost.lambda do what you need, you can submit a patch to operator_return_type_traits.hpp
adding support for boost::array