[Lemon-user] Graphs need first and next?

[Alpár Jüttner]

Hi Ben,

> Another thing that caused me a lot of problems is the fact that Arcs are 
> implicitly convertible to Edges. 

This is an unavoidable feature as it allows running algorithms like
Dijkstra on an undirected graph by making possible to pass an EdgeMap to
an algorithm which would expect an ArcMap as its input (such as the
costs for Dijkstra).

Regards,
Alpar