Re: [Boost-users] [Phoenix][v3] Argument/State dependent return type of actors?

On 01/-10/-28163 08:59 PM, Josef Weinbub wrote:

Hi

Recently I made myself familiar with Phoenix v3, more specifically with actors. I did a few test implementations, and I wondered if there is a way to access the argument types (nested in the context's environment) and/or the type of the state(s) (nested in the proto expression) for the actor's result type declaration.

.... Hi again! Indeed I have overlooked something, being 'result_of' ... as provided by the Boost Utility library and adopted by the C++11 standard. Sorry for that, should have known .. In case someone else wonders how to approach my problem, checkout the Boost.Utility::result_of documentation: http://www.boost.org/doc/libs/1_48_0/libs/utility/utility.htm#result_of One has to nest a result struct with the functors parameter types in the Boost.Phoenix actor's evaluation functor. For the sake of completeness, in the following my previous evaluation functor is depicted again, but instead of the static "typedef int result_type; " we now use the nested result struct: struct myactor_eval { template<class> struct result; template struct result { // here we can relate the return type both to the state type // and to the functor's argument types ... typedef ..... type; }; template typename myactor_eval::result< myactor_eval(StateExpr, Context) >::type operator()(StateExpr const& state_expr, Context & ctx) const { return ...; } }; Best, Josef PS: Thank you, Joel, for noticing my post and forwarding it to Thomas - much appreciated!