HaskellForMaths-0.4.1: Combinatorics, group theory, commutative algebra, non-commutative algebra

Math.Combinatorics.Graph

Description

A module defining a polymorphic data type for (simple, undirected) graphs, together with constructions of some common families of graphs, new from old constructions, and calculation of simple properties of graphs.

Synopsis

# Documentation

combinationsOf :: Integral t => t -> [a] -> [[a]]Source

combinationsOf k xs returns the subsets of xs of size k. If xs is in ascending order, then the returned list is in ascending order

data Graph a Source

Datatype for graphs, represented as a list of vertices and a list of edges. For most purposes, graphs are required to be in normal form. A graph G vs es is in normal form if (i) vs is in ascending order without duplicates, (ii) es is in ascending order without duplicates, (iii) each e in es is a 2-element list [x,y], x<y

Constructors

 G [a] [[a]]

Instances

 Functor Graph Eq a => Eq (Graph a) Ord a => Ord (Graph a) Show a => Show (Graph a)

nf :: Ord a => Graph a -> Graph aSource

Convert a graph to normal form. The input is assumed to be a valid graph apart from order

graph :: Ord t => ([t], [[t]]) -> Graph tSource

Safe constructor for graph from lists of vertices and edges. graph (vs,es) checks that vs and es are valid before returning the graph.

nullGraph :: Integral t => t -> Graph tSource

The null graph on n vertices is the graph with no edges

The null graph, with no vertices or edges

c :: Integral t => t -> Graph tSource

c n is the cyclic graph on n vertices

k :: Integral t => t -> Graph tSource

k n is the complete graph on n vertices

kb :: Integral t => t -> t -> Graph tSource

kb m n is the complete bipartite graph on m and n vertices

kb' :: Integral t => t -> t -> Graph (Either t t)Source

kb' m n is the complete bipartite graph on m left and n right vertices

q :: Integral t => Int -> Graph tSource

q k is the graph of the k-cube

q' :: Integral t => Int -> Graph [t]Source

fromDigits :: Integral a => Graph [a] -> Graph aSource

Given a graph with vertices which are lists of small integers, eg [1,2,3], return a graph with vertices which are the numbers obtained by interpreting these as digits, eg 123. The caller is responsible for ensuring that this makes sense (eg that the small integers are all < 10)

fromBinary :: Integral a => Graph [a] -> Graph aSource

Given a graph with vertices which are lists of 0s and 1s, return a graph with vertices which are the numbers obtained by interpreting these as binary digits. For example, [1,1,0] -> 6.

restriction :: Eq a => Graph a -> [a] -> Graph aSource

The restriction of a graph to a subset of the vertices

inducedSubgraph :: Eq a => Graph a -> [a] -> Graph aSource

isRegular :: Eq t => Graph t -> BoolSource

A graph is regular if all vertices have the same valency (degree)

isCubic :: Eq t => Graph t -> BoolSource

A 3-regular graph is called a cubic graph

distance :: Eq a => Graph a -> a -> a -> IntSource

Within a graph G, the distance d(u,v) between vertices u, v is length of the shortest path from u to v

diameter :: Ord t => Graph t -> IntSource

The diameter of a graph is maximum distance between two distinct vertices

girth :: Eq t => Graph t -> IntSource

The girth of a graph is the size of the smallest cycle that it contains. Note: If the graph contains no cycles, we return -1, representing infinity.

isConnected :: Ord t => Graph t -> BoolSource

Is the graph connected?

kneser :: Integral t => t -> t -> Graph [t]Source

kneser n k returns the kneser graph KG n,k - whose vertices are the k-element subsets of [1..n], with edges joining disjoint subsets