Subject: Re: [boost] [gsoc-2013] Boost.Expected
From: Gottlob Frege (gottlobfrege_at_[hidden])
Date: 2013-04-24 18:08:11
On Wed, Apr 24, 2013 at 5:29 PM, Vicente J. Botet Escriba <
> Le 24/04/13 19:49, Gottlob Frege a écrit :
> On Wed, Apr 24, 2013 at 12:47 PM, Vicente J. Botet Escriba <
>> vicente.botet_at_[hidden]> wrote:
>> Le 24/04/13 18:02, Gottlob Frege a écrit :
>>> One thing I missed in this conversation:
>>>> Are we considering the Alexandrescu behaviour of throwing in the
>>>> if the expected<> has not been read?
>>>> Why would you want to that?
>> I didn't say I did, but some might. And the Alexandrescu version (which
>> was referenced as one design) works that way.
> I didn't understood it this way. I've checked the slides and I have not
> found nothing about the destructor. Could you point me where have you found
> that the destructor throws if the value were not read?
Sorry, I must have been thinking of a different Alexandrescu class. He
has/had an error class where if you didn't read the error, it threw in the
destructor. I was inadvertently mixing the two concepts together.
>>> I was imagining just an excepted<likely_type, error_type> class. I
>>>> about the novel throwing behaviour.
>>>> This will correspond to expected_or_error.
>>> I'm hoping for just one class, not multiple.
> I didn't catch that you were suggesting to have
> template <typename T, typename ExceptionalType= std::exception_ptr>
> class expected;
> Humm, this could be done, but the has_exception function has no sense if
> the ExceptionalType is not exception_ptr.
> But a get_exceptional and accept_exceptional_visitor have sense in both
I'm just thinking that having the error be an exception is too specific.
I'd prefer a single class where the error might just be an error code, or
might be a full exception of some kind. *If* we could give it reasonable
behaviour for both cases. (Or compromise.) Otherwise we have multiple
expected_* classes, which I think lowers the value of each (in this case).
Maybe separate classes is best, but I suspect that a single class would
have a better chance of eventual standardization.
But I should probably just stop commenting, and wait and see what comes out
of this. I'm having a hard time (and have a lack of time) following this,
so once the class is more concrete it should be easier to discuss.
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