module Make:
Parameters: 

val fold : (G.V.t > 'a > 'a) > Topological.G.t > 'a > 'a
fold action g seed
allows iterating over the graph g
in topological order. action node accu
is called repeatedly,
where node
is the node being visited, and accu
is the result of
the action
's previous invocation, if any, and seed
otherwise.
If g
contains cycles, the order is unspecified inside the cycles and
every node in the cycles will be presented exactly once.
Not tailrecursive. Complexity: O(V+E)
val iter : (G.V.t > unit) > Topological.G.t > unit
iter action
calls action node
repeatedly. Nodes are (again)
presented to action
in topological order.
The order is the same as for fold
.