Re: [boost] [next gen future-promise] What to call the monadic return type?

On 25 May 2015 at 15:44, Avi Kivity wrote:

I believe error_code is unneeded. Exceptions are expected to be slow. If you want another type of variant return, let the user encapsulate it in T (could be optional<T>, or expected, or whatever).

Please read the rationale at https://svn.boost.org/trac/boost/wiki/BestPracticeHandbook#a8.DESIGN:S tronglyconsiderusingconstexprsemanticwrappertransporttypestoreturnstat esfromfunctions as was requested. In particular, error_code is fast, and unexpected returns are not exceptional and must be as fast as expected returns. Also, any monadic transport would default construct to an unexpected state of a null error_code in fact, which is constexpr. This lets one work around a number of exception safety irritations where move constructor of T is not noexcept more easily.

...

... turns into a "mov $5, %eax", so future<T> is now also a lightweight monadic return transport capable of being directly constructed.

Can you post the code? I'd be very interested in comparing it with seastar's non-allocating futures.

I may do so once I've got the functioning constexpr reduction being unit tested per commit. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/