Re: [boost] shared_ptr<>: why no operator[] ? [SEC=UNCLASSIFIED]

Subject: Re: [boost] shared_ptr<>: why no operator[] ? [SEC=UNCLASSIFIED]
From: Levy, Gabriel (Contractor) (Gabriel.Levy_at_[hidden])
Date: 2011-07-27 05:35:04

UNCLASSIFIED

Note!!!

The following statement 

boost::shared_ptr<int> p(new int(42));

is NOT allocating an array of int, it allocates only 1 int and
initialises it to the value of 42.

To instantiate an array the statement would have to use .... (new
int[42]) 
 
So the doco you refered to IS correct.
Hope this clarifies it...

Gabe Levy
Senior Software Engineer, Contractor, Estrings Pty Ltd

-----Original Message-----
From: boost-bounces_at_[hidden]
[mailto:boost-bounces_at_[hidden]] On Behalf Of dgwsoft
Sent: Wednesday, 27 July 2011 6:37 PM
To: boost_at_[hidden]
Subject: Re: [boost] shared_ptr<>: why no operator[] ?

Neil Groves-3 wrote:
> 
> On Tue, Jul 26, 2011 at 11:39 PM, dgwsoft &lt;gareth_at_[hidden]&gt;
> wrote:
> 
>> boost::shared_ptr<int> p(new int(42));
>>
>> To access elements of the array I can do:
>>
>> p.get()[10] = 7;
>>
>> But wouldn't it be nicer to do:
>>
>> p[10] = 7; // ?
>>
>> So: why is no T& operator[](int) defined for shared_ptr ? I'm just 
>> interested in the design reasons for this.
>>
>>
> This isn't guaranteed to properly destroy the array. It will call 
> delete, rather than delete[].
> This is why there is also boost::shared_array which is what you should

> be using and has an operator[].
> 

Thanks, Neil, that makes perfect sense. One should never do:

boost::shared_ptr<int> p(new int(42));

In which case, someone should look at this page:
http://www.boost.org/doc/libs/1_47_0/libs/smart_ptr/shared_ptr.htm#examp
le

(under Thread Safety) which is where I copied that code from.

cheers

Gareth

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