Joel de Guzman wrote:
Ok, tell you what: I understand the confusion. If you or anyone else can find a way to do value_at that passes the exact underlying element (undecorated) type, through the transform function, then, I'd gladly rethink this matter. Here's a possibility:
struct identity { template <class FunCall> struct result;
template <class Fun, class T> struct result<Fun(T&)> { typedef T& type; };
template <class T> struct value { typedef T& type; };
template <class T> T& operator()(T& v) const { return v; } };
I think this is not a good solution. If we are following Boost.Iterator's way, "value concept" should be placed in not FunctionObject but in transform_view. Because boost::transform_iterator can't always determine its `value_type` or `reference` from FunctionObject, you can pass explicitly `value_type` and `reference` type to boost::transform_iterator. Say, template<class Seq, class F, class ResultOfDeref = use_default, class ValueOf = use_default> struct transform_view; seems better. Regards, -- Shunsuke Sogame