Jeff,

Jeffrey Lee Hellrung, Jr. wrote:

Nathan Crookston wrote:

1. Both this and Michel's suggestions require C++11 features -- either decltype or rvalue references.  Extended transformed allows the creation of a result_binder struct to be delayed until the reference type of the input range is available.  This would make it usable for non-lambda instances where an explicit return type is desired without the fuss of defining a separate functor (assuming the functor to be wrapped cannot be changed).  I believe a correct C++03 version of result_binder would need a large number of operator() overloads depending on how many arguments it intends to forward.

True, though this sounds like more of an implementation concern (don't get me wrong, it's a valid concern) than a capability concern.

Agreed.  I think there's also slightly more mental drag involved with a result_binder call, especially if I also need to remember where it resides to #include it.  But that's minor.

2. Such a syntax (transformed<R>(...)) has been used previously -- boost bind's docs, referring to bind<R> syntax, state:  "It is generally used with function objects that do not, or cannot, expose result_type."[1]  Without begging for an Emerson quote, I believe consistency with bind in this case will improve the usability enough to justify the required changes.  Note also that this is the only current adaptor[2] which takes a function object with arbitrary return type (others must return something which is convertible to bool).  Note also that the changes are a pure extension (previous usage continues unchanged).

I'm personally not swayed but it's a fair rationale nonetheless and ultimately your call since I'm not doing it :)

I've done all I plan to, unless a maintainer decides it's worth using and would like some changes.  Just to be clear, Nathan Ridge has been proposed as a sub-maintainer, not myself.  (FWIW, I think he's an excellent choice for that position.)