Re: [boost] Interest in an 'either' library?

Subject: Re: [boost] Interest in an 'either' library?
From: Larry Evans (cppljevans_at_[hidden])
Date: 2013-06-25 10:27:08

On 06/24/13 22:55, David Sankel wrote:
> On Mon, Jun 24, 2013 at 1:19 PM, Eric Niebler <eniebler_at_[hidden]> wrote:
> 
>> On 13-06-24 11:53 AM, Pierre Talbot wrote:
>>>>
>>>> This misses what is, IMO, the most important use case of Haskell's
>>>> Either monad: automatic error propagation. This would be more useful if
>>>> there were a way to call a function such that if any of the function's
>>>> arguments were an Either-in-error, the function would immediately return
>>>> the error.
>>>>
>>>> I implemented something like this. Check out substitution_failure and
>>>> try_call starting here:
>>>>
>>>>
>> https://github.com/ericniebler/proto-0x/blob/master/boost/proto/v5/utility.hpp#L742
>>>
>>> In the Expected proposal, there are some methods related to this idea.
>>
>>
> <snip various do-syntax derivatives>
> 
> If we really care about adding a do syntax EDSL, why not make it general
> purpose like Haskell's version so that it can work with any monad and
> compose better with other things?
> 
> either<error, int> result =
>   do(
>     set( _x, getInt ),
>     set( _y, getInt ),
>     doReturn( pure( _x + _y ) ) );
> 
> If we're going to do that, lets do it generically and completely.
> 
> 
+1

David, is there source code demonstrating this do syntax?
Could you show how to do Eric's example with this do syntax?

-regards,
Larry