[Lemon-user] Copy constructors

[Alpár Jüttner]

Hi,

One more think you might find useful. Even if EdgeMap<> had default and
copy constructors, using

std::vector<lemon::ListGraph::EdgeMap<float> > edgeCostVec;

would not probably be a good idea. The problem is that when you enlarge
an std::vector<>, it copies all its elements from time to time. It
results in copying the full EdgeMap<>s, which are typically large data
structures.

To the contrary, 

std::vector<lemon::ListGraph::EdgeMap<float>* > edgeCostVec;

copies the pointers only, the maps themselves remain in place.

Regards,
Alpar



On Tue, 2010-02-23 at 07:15 -0800, D Haley wrote:
> Hello again,
> 
> I am having more troubles with edgemaps (thanks for the prev. help, worked a treat). Due to the library interface, the copy constructors are private for edgemaps, which seem to prevent me assigning or dupliating them in any way. Is there a way I can do something like the following? I'm currently dropping to pointer semantics, but it feels like a kludge.
> 
>         vector<lemon::ListGraph> g;
>         vector<lemon::ListGraph::EdgeMap<float> > edgeCostVec;
> 
>         makeSomeGraphs(g); //pass-by-ref (non-const)
> 
>         edgeCostVec[ui].resize(g.size());
>         for(unsigned int ui=0;ui<g.size(); ui++)
>                 edgeCostVec[ui] = (lemon::ListGraph::EdgeMap<float>(g[ui]));
> 
> 
> 
>       
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