[snip]
Hi Hans,
I believe the problem is to do with the inductive nature of the FGL library. A graph in FGL is a series of contexts, each corresponding to a node. Each context contains lists of links to/from the latest node to nodes in previous contexts. Each link is only recorded once, and whether it appears in the context for the source or destination node depends on the order that the graph is constructed. Ah, that was my mistake! I thought a context was an 'in' adjacency list, a node, a label and and 'out' adjacency list, and this for each node. So each link would be recorded twice! Based on this assumption I tried to, and thought I did, construct a new unconnected graph.
[snip] Based on the idea that gsel didn't work as I expected, I already found a workaround, but your example solutions look better. I'll look at my code again. Many thanks for your helpful reply! Best Regards, Hans van Thiel