Re: [boost] [optional] Why was optional<T>::reset() deprecated?

Subject: Re: [boost] [optional] Why was optional<T>::reset() deprecated?
From: Andrzej Krzemienski (akrzemi1_at_[hidden])
Date: 2016-03-02 06:30:47

2016-03-02 12:21 GMT+01:00 Beman Dawes <bdawes_at_[hidden]>:

> On Wed, Mar 2, 2016 at 3:20 AM, Andrey Semashev <andrey.semashev_at_[hidden]
> >
> wrote:
>
> > On 2016-03-02 01:51, Andrzej Krzemienski wrote:
> >
> >> At some earlier stages of development, boost::optional did not have the
> >> assignment from boost::none_t (and probably also from T); and reset was
> >> the
> >> only way to efficiently change the optional from the state of having the
> >> value to the state of not having the value.
> >>
> >> After the addition of more fancy syntax (conversion to bool, assignment
> >> from none_t), reset() (and is_initialized()) became redundant, and hence
> >> the deprecation.
> >>
> >> I got that from reading Boost mailing archives once.
> >>
> >
> > FWIW, I don't think that having support for 'none' is enough reason to
> > deprecate 'reset' (same for 'is_initialized'). I know some of my
> colleagues
> > who prefer these methods to the fancy syntax because it feels more
> aligned
> > with other Boost and standard library components. Having 'reset' also
> > allows not to include boost/none.hpp.
> >
>
> The standards committee's library enhancements working group (LEWG) agrees
> with you. Nevin's question came up in the context of aligning several
> Library Fundamentals TS functions with each other and the rest of the
> standard library. The proposal is progressing and will likely be part of
> C++17.

P0032 <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0032r1.pdf>
mentions reset() with no arguments. I can un-deprecate this overload when
the proposal is accepted. I am not sure about the overload with T: we have
a more generalized emplace() for this purpose.

Regards,
&rzej