A wrapper around the types and functions from Data.Graph to make programming with them less painful. Also
implements some extra useful goodies such as
sccGraph, and improves the documentation of
the behaviour of some functions.
As it wraps Data.Graph, this module only supports directed graphs with unlabelled edges.
Incorporates code from the
containers package which is (c) The University of Glasgow 2002 and based
on code described in:
Lazy Depth-First Search and Linear Graph Algorithms in Haskell, by David King and John Launchbury
- type Edge i = (i, i)
- data Graph i v
- vertex :: Ord i => Graph i v -> i -> v
- fromListSimple :: Ord v => [(v, [v])] -> Graph v v
- fromList :: Ord i => [(i, v, [i])] -> Graph i v
- fromListLenient :: Ord i => [(i, v, [i])] -> Graph i v
- fromListBy :: Ord i => (v -> i) -> [(v, [i])] -> Graph i v
- fromVerticesEdges :: Ord i => [(i, v)] -> [Edge i] -> Graph i v
- toList :: Ord i => Graph i v -> [(i, v, [i])]
- vertices :: Graph i v -> [i]
- edges :: Graph i v -> [Edge i]
- successors :: Ord i => Graph i v -> i -> [i]
- outdegree :: Ord i => Graph i v -> i -> Int
- indegree :: Ord i => Graph i v -> i -> Int
- transpose :: Graph i v -> Graph i v
- reachableVertices :: Ord i => Graph i v -> i -> [i]
- hasPath :: Ord i => Graph i v -> i -> i -> Bool
- topologicalSort :: Graph i v -> [i]
- depthNumbering :: Ord i => Graph i v -> [i] -> Graph i (v, Maybe Int)
- data SCC i
- stronglyConnectedComponents :: Graph i v -> [SCC i]
- sccGraph :: Ord i => Graph i v -> Graph (Set i) (Map i v)
- traverseWithKey :: Applicative t => (i -> a -> t b) -> Graph i a -> t (Graph i b)
A directed graph
Morally, the inverse of
fromList. The order of the elements in the output list is unspecified, as is the order of the edges
in each node's adjacency list. For this reason,
toList . fromList is not necessarily the identity function.
Find the vertices we can reach from a vertex with the given indentity
The graph formed by flipping all the edges, so edges from i to j now go from j to i
List all of the vertices reachable from the given starting point
Is the second vertex reachable by following edges from the first vertex?
It is worth sharing a partial application of
hasPath to the first vertex if you are testing for several
vertices being reachable from it.
Topological sort of of the graph (http://en.wikipedia.org/wiki/Topological_sort). If the graph is acyclic, vertices will only appear in the list once all of those vertices with arrows to them have already appeared.
Vertex i precedes j in the output whenever j is reachable from i but not vice versa.
Number the vertices in the graph by how far away they are from the given roots. The roots themselves have depth 0,
and every subsequent link we traverse adds 1 to the depth. If a vertex is not reachable it will have a depth of
Strongly connected components (http://en.wikipedia.org/wiki/Strongly_connected_component).
The SCCs are listed in a *reverse topological order*. That is to say, any edges *to* a node in the SCC originate either *from*:
1) Within the SCC itself (in the case of a
2) Or from a node in a SCC later on in the list
Vertex i strictly precedes j in the output whenever i is reachable from j but not vice versa. Vertex i occurs in the same SCC as j whenever both i is reachable from j and j is reachable from i.
The graph formed by the strongly connected components of the input graph. Each node in the resulting graph is indexed by the set of vertex indices from the input graph that it contains.