Merge 102c57b into e097454

gap/examples.gd

@@ -48,3 +48,7 @@ DeclareOperation("PetersenGraph", [IsFunction]);
 DeclareConstructor("GeneralisedPetersenGraphCons", [IsDigraph, IsInt, IsInt]);
 DeclareOperation("GeneralisedPetersenGraph", [IsInt, IsInt]);
 DeclareOperation("GeneralisedPetersenGraph", [IsFunction, IsInt, IsInt]);
+
+DeclareConstructor("FolkmanGraphCons", [IsDigraph]);
+DeclareOperation("FolkmanGraph", []);
+DeclareOperation("FolkmanGraph", [IsFunction]);

gap/examples.gi

@@ -370,3 +370,18 @@ GeneralisedPetersenGraphCons);
 
 InstallMethod(GeneralisedPetersenGraph, "for integer, integer", [IsInt, IsInt],
 {n, k} -> GeneralisedPetersenGraphCons(IsImmutableDigraph, n, k));
+
+InstallMethod(FolkmanGraphCons, "for IsMutableDigraph", [IsMutableDigraph],
+function(filt)
+  return DigraphFromGraph6String(IsMutableDigraph,
+                                 "Sl?gHS?_g?oTS?AA_?GOT@O??_i_?G@@S");
+end);
+
+InstallMethod(FolkmanGraphCons, "for IsImmutableDigraph", [IsImmutableDigraph],
+filt -> MakeImmutable(FolkmanGraphCons(IsMutableDigraph)));
+
+InstallMethod(FolkmanGraph, [],
+{} -> FolkmanGraphCons(IsImmutableDigraph));
+
+InstallMethod(FolkmanGraph, "for a function", [IsFunction],
+filt -> FolkmanGraphCons(filt));

tst/standard/examples.tst

@@ -226,6 +226,28 @@ Error, the arguments <n> and <k> must be non-negative integers,
 gap> JohnsonDigraph(IsMutableDigraph, 4, 2);
 <mutable digraph with 6 vertices, 24 edges>
 
+#  Folkman
+gap> D := FolkmanGraph();
+<immutable digraph with 20 vertices, 80 edges>
+gap> DigraphNrVertices(D) = 20;
+true
+gap> DigraphNrEdges(D) = 80;
+true
+gap> Size(AutomorphismGroup(D)) = 3840;
+true
+gap> IsHamiltonianDigraph(D);
+true
+gap> ChromaticNumber(D);
+2
+gap> DigraphDiameter(D);
+4
+gap> IsBipartiteDigraph(D);
+true
+gap> IsRegularDigraph(D);
+true
+gap> D := FolkmanGraph(IsMutableDigraph);
+<mutable digraph with 20 vertices, 80 edges>
+
 #
 gap> DIGRAPHS_StopTest();
 gap> STOP_TEST("Digraphs package: standard/examples.tst", 0);