Incidence Structures, Graphs and Codes

IncidenceStructure(G) : Grph -> Inc
Construct the incidence structure D corresponding to the graph G, where the blocks of D correspond to the edges of G.
PointGraph(D) : Inc -> Grph
The point graph G of the incidence structure D. The graph G has the same point set as D and two vertices u and v of G are adjacent whenever there is a block of D containing both u and v.
BlockGraph(D) : Inc -> Grph
The block graph of the incidence structure D, i.e., the point graph of the dual of D.
IncidenceGraph(D) : Inc -> Grph
The incidence graph of the incidence structure D. This bipartite graph has as vertex set the union of the point set P and block set B of D. A vertex p ∈P is adjacent to a vertex b ∈B whenever p ∈b.
LinearCode(D, K) : Inc, FldFin -> Code
Given an incidence structure D with v points and a finite field K, this function returns the linear code C of length v generated by the characteristic functions of the blocks of D considered as vectors of the K-space K(v).

Example Design_graphs (H156E12)

The linear code of the Witt 5-(24, 8, 1) design over GF(2) is the extended Golay code over GF(2).
> D := WittDesign(24);
> C := LinearCode(D, GF(2));
> C eq GolayCode(GF(2), true);
true
V2.28, 13 July 2023