Graph library
Graphlib is a generic library that extends a well known OCamlGraph library. Graphlib uses its own, more reach, Graph interface that is isomorphic to OCamlGraph's Sigs.P signature for persistant graphs. Two functors witness the isomorphism of the interfaces: Graphlib.To_ocamlgraph and Graphlib.Of_ocamlgraph. Thanks to these functors, any algorithm written for OCamlGraph can be used on Graphlibs graph and vice verse.
The Graph interface provides a richer interface in a Core style. Nodes and Edges implements Opaque data structure, i.e., they come with Maps, Sets, Hashtbls, etc, preloaded (e.g., G.Node.Set is a set of node for graph implementation, provided by a module named G). Graphs also implement Printable interface, that makes them much easier to debug.
Along with graphs, auxiliary data structures are provided, like path to represent paths in graph, tree for representing different graph spannings, partition for graph partitioning, and more.
Graphlib is a library that provides a set of generic algorithms, as well as implementations of a Graph interface, and a suite of preinstantiated graphs.
Contrary to OCamlGraph, each Graphlib interface is provided as a function, not a functor. Thus making there use syntactically easier. Also, Graphlib heavily uses optional and keyword parameters. For die-hards, many algorithms still have functor a interface.
All Graphlib algorithms accept a first-class module with graph implementation as a first argument. You can think of this parameter as an explicit type class. Later, when modular implicits will be accepted in OCaml, this parameter can be omitted. But for now, we need to pass them.
A recommended way to work with Graphlib is to bind the chosen implementation with some short name, usually G would be a good choice:
module G = Graphlib.Make(String)(Bool)
This will bind name G with a graph implementation that has string nodes, with edges labeled by values of type bool.
To create a graph of type G.t one can use a generic Graphlib.create function:
let g = Graphlib.create (module G) ~edges:[
"entry", "loop", true;
"loop", "exit", true;
"loop", "loop", false;
] ()
This will create an instance of type G.t. Of course, it is still possible to use non-generic G.empty, G.Node.insert, G.Edge.insert.
module type Node = sig ... endmodule type Edge = sig ... endInterface that every Graph edge should provide
module type Graph = sig ... endtype ('c, 'n, 'e) graph =
(module Graph
with type edge = 'e
and type node = 'n
and type t = 'c)a type abbreviation for a packed module, implementing graph interface. Note: this type prenexes only 3 out of 8 type variables, so, sometimes it is not enough.
type edge_kind = [ | `Tree| `Back| `Cross| `Forward
]Graph edges classification. For explanations see DFS.
a result of partitioning algorithms
walk without a repetition of edges and inner nodes
module Tree : sig ... endTree is a particular subtype of a graph for which each node has only one predecessor, and there is only one path between tree root and any other node. Here is an example of a tree:
Frontier maps each node into a possibly empty set of nodes. This is used for representing dominance and post-dominance frontiers.
module Path : sig ... endResult of a set partitioning.
module Group : sig ... endGroup is a non-empty set that is a result of partitioning of an underlying set S into a set of non-intersecting and non-empty subsets that cover set S. See Partition for more information.
module Equiv : sig ... endOrdinal for representing equivalence. Useful, for indexing elements based on their equivalence.
Auxiliary graph data structures
Isomorphism is a bijection between type s and t. Usefull for creating graph views and mapping graphs. See Graphlib.view and Graphlib.Mapper.
Visual attributes for graph vizualization.
Consult OCamlGraph library for more information.
type ('n, 'a) labeled = {node : 'n;node_label : 'a;
}A solution to a system of fixed-point equations.