Re: [Boost-users] using shared_array in Nd array

From: Jeffrey Jiang (gamedboy_at_[hidden])
Date: 2007-08-31 23:08:15

Thanks for the reply. I agree that this way is prob clearer and predictable.
However in this case I am implementing a fix size grid of pointers, to 
represent a geographical map, and the location of the pointer to determine 
the position of the character.

So although using vector in this case would work, it will convey a wrong 
message to the users that
-they can resize the grid
-the location of the pointer is not impt

I would rather use a shared_ptr<Character> **characterGrid instead, which 
bring us back to the problem below.

Jeffrey.

"James Emerton" <ephelon_at_[hidden]> wrote in message 
news:c9424d940708310855t3d5acd1boef1c2686bfabfca5_at_mail.gmail.com...
> Do you really need to have a shared_array containing shared_ptrs?
>
> You would probably be better off with something like:
>
> std::vector< std::vector< boost::shared_ptr<Character> > > characterGrid;
> characterGrid.resize( _info.l );
> for( int i = 0; i < _info.l; ++i )
>  characterGrid.resize( _info.w );
>
> James
>
>
>
> On 8/30/07, Jeffrey Jiang <gamedboy_at_[hidden]> wrote:
>
>> This is a sparse array, most of the pointers will be set to 0. As I could
>> not find much information about shared_array on line, I would like to 
>> check
>> is there any issue with this implementation.
>>
>> boost::shared_array<boost::shared_array<boost::shared_ptr<Character>>>
>> characterGrid(new
>> boost::shared_array<boost::shared_ptr<Character>>[_info._l ]);
>>
>> for( int i=0;i< _info._l; i++) {
>>
>>     characterGrid[i] = 
>> boost::shared_array<boost::shared_ptr<Character>>(new
>> boost::shared_ptr<Character>[_info._w]);
>>
>>     for( int j=0; j< _info._w; j++) {
>>
>>         //is it alright for me to use an empty shared_ptr in this context 
>> to
>> init the array?
>>
>>         characterGrid[i][j] = boost::shared_ptr<Character>();
>>
>>     }
>>
>> }
>>