> I am converting some code from SICStus Prolog, and need a directed graph
> library for Ocaml. Any pointers?

It is difficult to design a `universal' graph library, i.e. one that will suit
most users' needs, because different applications often require different
concrete representations of graphs.

Perhaps (as suggested by Chris Tilt in an earlier message) the best route is
to write a functorized library of graph algorithms, where each algorithm is
written independently of the actual data structure used to represent the
graph.

Yet, even then, it is not easy to determine which set of basic operations
should be supported by the structure. For instance, some algorithms are easily
expressed if graph nodes are numbered sequentially, but this is a rather
undesirable requirement if nodes are to be dynamically added and deleted.  As
another example, some algorithms can be written more efficiently if they are
allowed to store data directly within every graph node, but this causes them
to be non-reentrant and can also be a problem in some applications.

As an example of this functorized style of programming, attached is an
abstract implementation of a topological-order iterator for graphs.

-- 
François Pottier
Francois.Pottier@inria.fr
http://pauillac.inria.fr/~fpottier/