Added IsOrderFilter

digraphs · Nov 27, 2024 · 6de8243 · 6de8243
1 parent c0a8e1b
commit 6de8243
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diff --git a/gap/oper.gd b/gap/oper.gd
@@ -142,6 +142,7 @@ 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
@@ -2312,6 +2312,11 @@ 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)