Re: [boost] [optional] layout

Subject: Re: [boost] [optional] layout
From: Gottlob Frege (gottlobfrege_at_[hidden])
Date: 2009-10-28 11:58:54

> that is not the same thing as gottlob was proposing.

What Domagoj was asking for was:
...because that is what i was whishing for to be extracted from optional<> -
the placement new/in-place construction + aligned storage + reference
workarounds&co. wrapped up machinery...

with examples of uses.  I gave another example of where those
internals could be useful, and what I ended up doing.

> boost::optional<> doesn't
> have the problems herb sutter lists, and a type that is only used for in
> place construction, without optional's conditional bool, wouldn't either.
>

agreed.  I was off on a tangent about just my example.

> I've been missing such a type, too, but I think it should be part of the boost
> in place utility instead of boost::optional:
> http://www.boost.org/doc/libs/1_35_0/libs/utility/in_place_factories.html
>
> see "container-side usage" there.

Yes, in-place is again similar.  At least it handles the construction
issues.  I see it as either my templates have 10 overloads, or I use
in_place (easier for me) and make my users use it as well (bit harder
for them).  For a fast_impl, the user is probably another library
writer, already doing forwarding, so I don't see that as a problem.

Definitely lots of code doing similar things - more reasons why it
could maybe be split up / reorganized / grouped / etc.

Of course, C++0x vararg templates + 'perfect forwarding' would make
things easier and change much of this.

Tony