Re: [boost] [outcome v2] Please comment on new result<T, EC> reference API docs

Subject: Re: [boost] [outcome v2] Please comment on new result<T, EC> reference API docs
From: Peter Dimov (lists_at_[hidden])
Date: 2017-06-22 01:08:14

Niall Douglas wrote:
> The idea, since we no longer have variant storage, is to see if we'd like 
> to implement
>
> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0262r0.html
> (except with the parameter order reversed).

I'm not particularly enthusiastic about status_value (and the argument given 
in the paper is unconvincing.) Neither am I thrilled by the idea of 
result<R, void> (an optional) or result<void, void> (something like a 
glorified pair<bool, bool>.)

result<T, EC> in its original form represented a very clear concept: the 
type of a function that must either return a value, or a reason for the lack 
of value. All of the above do not fit this concept and to me ring hollow.

The fact that for outcome<T, EC, exception_ptr> we may want to have both an 
EC and an exception_ptr does not necessarily mean that we need to give up on 
the Either( Value, Reason ). In outcome's case, the reason is just more 
elaborate.