module Topological:Topological order.sig..end
This functor provides functions which allow iterating over a graph in
topological order.
module type G =sig..end
module Make:
module Make_stable:
Topological.Make, except that the resulting
topological ordering is stable according to vertices comparison: if two
vertices v1 and v2 are topologically equal, v1 is presented first to
the iterator if and only if G.V.compare v1 v2 <= 0.