merge semantics is not clear

[osa1]

Documentation says this:

  -- | Merge the 'Context' into the 'DynGraph'.
  --
  --   Contexts should only refer to either a Node already in a graph
  --   or the node in the Context itself (for loops).

Without looking at an implementation it's not clear to me what what does "merge" mean in this context. I think this could use more sentences. More specifically, I think it's worth adding that merge is for adding new stuff and updating labels, and it's not possible to remove an edge using it. Also, when a new edge A -> B added using this, predecessors of B is automatically updated.

Since DynGraph is a typeclass I think these should be specified so that using a different implementation would not break the program

[ivan-m]

Well, it's for adding a node and edges associated with it, not for updating labels.

I'll have a look, but I'm not sure how much clearer this can be; some fundamental knowledge as to how inductive graphs work is required, and from the definition of a Context it should be clear that it can't remove any existing edges.