purescript-digraph

A directed graph library for PureScript.

The directed graph pictured above can be represented with an AdjacencyList. An adjacency list is a list of tuples that contain a vertex and a list of edges to its adjacent vertices. A Graph can be constructed from an AdjacencyList.

let edges = fromFoldable $
  [ Tuple 'A' (fromFoldable [Tuple 'B' 1, Tuple 'C' 2])
  , Tuple 'B' (fromFoldable [Tuple 'A' 1, Tuple 'D' 3])
  , Tuple 'C' (fromFoldable [Tuple 'A' 2, Tuple 'D' 4])
  , Tuple 'D' (fromFoldable [Tuple 'B' 3, Tuple 'C' 4])
  , Tuple 'E' (fromFoldable [Tuple 'F' 1])
  , Tuple 'F' (fromFoldable [Tuple 'E' 1])
  , Tuple 'G' (fromFoldable [])
  ]

let graph = fromAdjacencyList edges

The size function returns the number of vertices in a graph.

size graph
-- 7

The vertices function returns a list of the vertices in a graph.

vertices graph
-- ['A', 'B', 'C', 'D', 'E', 'F', 'G']

The isAdjacent function returns true if two vertices are connected by an edge.

isAdjacent 'A' 'B' graph
-- true

The weight function returns the weight of the edge between two vertices.

weight 'A' 'B' graph
-- Just 1

The adjacent function returns all vertices connected to a vertex by an edge. The adjacent' function will also include the weight of the edges.

adjacent 'A' graph
-- ['B', 'C']

adjacent' 'A' graph
-- [Tuple 'B' 1, Tuple 'C' 2]

The shortestPath function calculates the shortest path between two vertices using Dijkstra'a algorithm.

shortestPath 'A' 'D' graph
-- ['A', 'B', 'D']

The connectedComponents function calculates a list of connected components in a graph.

A connected component is a maximal subgraph in which any two vertices are connected to each other by a path.

connectedComponents graph
-- [Graph, Graph, Graph]

An empty graph can be constructed and updated.

(insertEdge 'A' 'B' 1 <<< insertVertex 'A' <<< insertVertex 'B') empty
-- Graph

Data.Graph