Re: [boost] [outcome] To variant, or not to variant?

Subject: Re: [boost] [outcome] To variant, or not to variant?
From: Robert Ramey (ramey_at_[hidden])
Date: 2017-06-01 22:07:16

On 6/1/17 11:30 AM, Peter Dimov via Boost wrote:
> Robert Ramey wrote:
>> or
>>
>> template<class T>
>> struct outcome : public std::variant<T, std::error_code> {
>> // some special member functions
>> outcome(const std::error_code & e){...} // construct as error
>> outcome(const T & t){...} // construct legitimate result
>> };
> 
> Something like this?
> 
> https://github.com/pdimov/variant2/blob/develop/include/boost/variant2/result.hpp 

Probably I suppose ....
> 
> 
> https://godbolt.org/g/EFGkCj

But this isn't really my point.  The point I'm trying to make is that 
all the design disputes are also found in variant.  It would seem to me 
that we're repeating all the same arguments ... with pretty much similar 
results.  If the problem is that variant (std, boost, ...) is "broken" 
or not suitable for that reason it would seem to me that THAT problem 
would need to be addressed.  Were that the case, then all the issues 
with outcome, optional, result, expected would disappear.  Maybe I'm 
over simplifying here, so feel free to demonstrate I'm wrong.  In any 
case, I would think that if a consensus can't be agreed upon after all 
this effort, maybe we should step back and except as a fact that 
"concensus cannot be reached".  So we'll permit variant implementations 
of variant either with policy or simpler yet, just a separate 
implementation.  Of course these separate implementations would also 
share a common base class so we get nested russian dolls.  But at least 
we don't get so much repetition.

Robert Ramey