Re: [Boost-users] [future] Confused about the represents in Doc "boost::future"

Subject: Re: [Boost-users] [future] Confused about the represents in Doc "boost::future"
From: chmhou_at_[hidden]
Date: 2015-02-15 20:46:39

Ok , I got the point , Thanks a lot



Martin
 
From: Ben Pope
Date: 2015-02-16 09:36
To: boost-users
Subject: Re: [Boost-users] [future] Confused about the represents in Doc "boost::future"
The part of the doc that says non-const& is wrong.
 
Elsewhere it says const&, which is correct.
 
Ben
 
 
 
On Monday, February 16, 2015 09:14 AM, chmhou_at_[hidden] wrote:
> Hi Ben
> Thanks for the replying.
>
> But it's seems like I didn't push my problem clearly .
> Let me make it simpler.
> how a non const reference of a value can guarantee multipe calls are safe ?
> e.g :
> first call return value like:
> string &first_ret = fun();
>
> second call return value like:
>
> string &second_ret = fun();
>
> because both "first_ret" and "second_ret" are not copy of the fun()
> return value, they are the right current value.
> so that we can say these calls are "safe" ?
> ------------------------------------------------------------------------
> Martin
>
>     *From:* Ben Pope <mailto:benpope81_at_[hidden]>
>     *Date:* 2015-02-16 00:03
>     *To:* boost-users <mailto:boost-users_at_[hidden]>
>     *Subject:* Re: [Boost-users] [future] Confused about the represents
>     in Doc "boost::future"
>     On Sunday, February 15, 2015 11:55 AM, Cheng Mo wrote:
>      > Hi all :
>      > I got confused in Doc of boost :: futures and I can't got the
>     point of
>      > sort of terms.
>      > The represents in Overvies of Futures like
>      > " Instances can be freely copied and assigned,
>      > and|boost::shared_future<R>::get()|
>      >
>     <http://www.boost.org/doc/libs/1_57_0/doc/html/thread/synchronization.html#thread.synchronization.futures.reference.shared_future.get>returns
>      > a non|const|reference so that multiple calls
>      > to|boost::shared_future<R>::get()|
>      >
>     <http://www.boost.org/doc/libs/1_57_0/doc/html/thread/synchronization..html#thread.synchronization.futures.reference.shared_future.get>are
>      > safe."
>      > no doubt that a const reference ..... are safe.
>      > a non const reference could be changed by external stimuli. isn't ?
>      > Or the key is "Instances can be freely copied" , so that we can
>     say "are
>      > safe"?
>     If you click on that link it says:
>     "shared_future<R>::get() returns a const reference to the value stored
>     in the shared state"
>     It's a typo, it should be const&, the contained value is not copied
>     when
>     the shared_future is copied.
>     Ben
>     _______________________________________________
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>
>
>
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>
 
 
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