Re: [Boost-users] [BGL] Troubles with floyd_warshall_all_pairs, johnson_all_pairs

From: Doug Gregor (dgregor_at_[hidden])
Date: 2007-07-03 11:26:56

On Jul 2, 2007, at 6:26 AM, Alex Ivanov wrote:
> //AFAIK it's impossible to declare array using directive below in  
> runtime:
>     double [xx][xx] D;
> //Compiler says the same:  "C2057: expected constant expression"
> //even code:
>     double [(const int)xx][(const int)xx] D;
> //won't work, so the only option left is to make a pointer:
>     double* D = new [xx*xx] ;
>
> //but both "floyd_warshall_all_pairs_shortest_paths" and
> "johnson_all_pairs_shortest_paths" are declared to take a  
> reference, not a
> pointer, so you'll get multiple compile errors, if you try to  
> compile like
> below:
>
> floyd_warshall_all_pairs_shortest_paths(G, D);

The DistanceMatrix is expected to be subscripted twice, so you would  
need something like:

        typedef double* double_array;

        double_array* D = new double_array[xx];
        for (int i = 0; i < xx; ++i)
                D[i] = new double [xx];

Or, you could use a vector of vectors:

        vector<vector<double> > D(xx, vector<double>(xx));

        - Doug