CGAL users discussion list

[Efraim Fogel <>]

 wrote:
> Hi all,
>
> The Arr_extended_dcel<Traits, VertexData, HalfedgeData, FaceData> class
> template allows to associate auxiliary data fields to the DCEL of an
> Arrangement_2. My question is how to extend only two of the three records (say
> with  VertexData and HalfedgeData) without wasting memory space for the last
> record (say FaceData) since it is not needed.
>
> Thanks in advance for your help,
> Hichem Barki
>
>   
You have two options:
1. Use Arr_extended_dcel<> with empty data records.
2. Develop your own extended DCEL. Start with the code in 
Arr_dcel_base.h, and remove those parts that you don't need. It's 
straight forward.

Option (1.) has a disadvantage: The compiler allocates a single byte for 
every empty nested construct. I believe that it is possible to improve 
Arr_extended_dcel using meta programming to avoid the empty byte.

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