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

Subject: Re: [boost] [next gen future-promise] What to call the monadic return type?
From: Peter Dimov (lists_at_[hidden])
Date: 2015-05-28 07:38:29

Vicente J. Botet Escriba wrote:

> I see that you want to be able to store error_code or exception_ptr.
> Wouldn't the interface of expected<T, variant<error_code, exception_ptr>> 
> be enough?

future<T> already adds the ability to store exception_ptr. There is no need 
to store another exception_ptr in the value. Niall's type is exactly 
equivalent to future<expected<T, error_code>>, as I already said (twice).

> I proposed to the C++ standard a function future<T>::next (bind) that 
> takes a continuation having T as parameter (future<R>(T)), and and 
> future<T>::catch_error that takes a as parameter a continuation that takes 
> an errror as parameter. The proposal was not accepted.

future<T>::next( [](T){...} ) is actually pretty useful, catch_error() much 
less so. You should have proposed just the former. (Sean Parent's future 
implementation's ::then has ::next's semantics IIRC.)