Re: [Boost-users] Use boost::shared_ptr with boost::adaptors

Subject: Re: [Boost-users] Use boost::shared_ptr with boost::adaptors
From: Robert Jones (robertgbjones_at_[hidden])
Date: 2012-05-01 04:09:23

On Mon, Apr 30, 2012 at 11:13 PM, Jeffrey Lee Hellrung, Jr. <
jeffrey.hellrung_at_[hidden]> wrote:

> On Mon, Apr 30, 2012 at 3:05 AM, Robert Jones <robertgbjones_at_[hidden]>wrote:
>
>> When you put it that way I can see your point, but just from the code the
>> OP presented the intermediate shared_ptr's should persist until
>> the end of the expression.
>>
>
> I'm not sure what you mean here; do you mean there's a bug on the boost
> side of the things in the original code listing?
>

Hmmm...., a bug... no... that might be overstating it I think. From your
imagined function it's just an intrinsic limitation of a
pragmatic implementation. But what I meant was that the OP's problematic
statement was

 boost::for_each(vec
                        | transformed(bind(&trasform, _1))
                        | indirected,
     bind(&foo::bar, _1));

which is a single expression, so it's reasonable to anticipate that
'temporary' shared_ptrs created in the course of evaluating
this expression should persist until the end of the expression. Ok, I know
there's lots of holes in that if you analyse it carefully,
not least that the shared_ptrs in question are not ever explicit, so the
rules aren't required to apply, but it might be reasonable to
expect that they would persist.

I'm really not nailing my colours to the mast here, just speculating, so be
gentle!

- Rob.