Added IsOrderFilter

digraphs · Oct 9, 2024 · d29873a · d29873a
1 parent bc224d1
commit d29873a
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diff --git a/gap/oper.gd b/gap/oper.gd
@@ -139,6 +139,7 @@ DeclareOperation("DigraphShortestPathSpanningTree", [IsDigraph, IsPosInt]);
 DeclareOperation("VerticesReachableFrom", [IsDigraph, IsPosInt]);
 DeclareOperation("VerticesReachableFrom", [IsDigraph, IsList]);
 DeclareOperation("IsOrderIdeal", [IsDigraph, IsList]);
+DeclareOperation("IsOrderFilter", [IsDigraph, IsList]);
 DeclareOperation("Dominators", [IsDigraph, IsPosInt]);
 DeclareOperation("DominatorTree", [IsDigraph, IsPosInt]);
 DeclareOperation("DigraphCycleBasis", [IsDigraph]);

diff --git a/gap/oper.gi b/gap/oper.gi
@@ -2076,6 +2076,11 @@ function(D, roots)
 
 end);
 
+InstallMethod(IsOrderFilter, "for a digraph and a list of vertices", [IsDigraph, IsList],
+function(D, roots)
+  return IsOrderIdeal(DigraphReverse(D), roots);
+end);
+
 InstallMethod(DominatorTree, "for a digraph and a vertex",
 [IsDigraph, IsPosInt],
 function(D, root)