Hi everyone, i think there is a bug in line_graph() function.
I tried it with some adjacency-matrix.
Here an example.
This is one of the matrix i used
0 1 0 0 0 1 0 0
1 0 1 1 0 0 0 0
0 1 0 0 0 1 0 0
0 1 0 0 1 0 1 0
0 0 0 1 0 1 0 0
1 0 1 0 1 0 0 1
0 0 0 1 0 0 0 1
0 0 0 0 0 1 1 0
a:from_adjacency_matrix (read_matrix("...path..."));
is_planar(a);
->true
la:line_graph(a);
is_planar(la);
->false
i think this line_graph should be planar..
MR