digraphs · fingolfin · Oct 1, 2026 · Oct 1, 2026 · Oct 1, 2026
diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
@@ -29,7 +29,6 @@ jobs:
           - stable-4.15
           - v4.14
           - v4.13
-          - v4.12
         mode:
           - onlyneeded
           - default
@@ -41,11 +40,6 @@ jobs:
             pkgs-to-clone: https://github.com/digraphs/graphviz.git https://github.com/gap-packages/NautyTracesInterface.git
             pkgs-to-build: io orb datastructures profiling grape NautyTracesInterface
 
-          - gap-version: v4.11 # Note: NautyTracesInterface requires GAP 4.12
-            mode: default # There wouldn't be much point testing GAP v4.11 with only needed packages. The only difference is whether Grape is loaded.
-            pkgs-to-clone: https://github.com/digraphs/graphviz.git
-            pkgs-to-build: io* orb* datastructures* profiling* grape*
-
     steps:
       - uses: actions/checkout@v7
       - name: Output g++ version . . .

diff --git a/PackageInfo.g b/PackageInfo.g
@@ -31,10 +31,6 @@ _STANDREWSMATHS := Concatenation(["Mathematical Institute, North Haugh, ",
 _STANDREWSCS := Concatenation(["Jack Cole Building, North Haugh, ",
                                "St Andrews, Fife, KY16 9SX, Scotland"]);
 
-if not CompareVersionNumbers(GAPInfo.Version, "4.12") then
-  IsKernelExtensionAvailable := fail;
-fi;
-
 SetPackageInfo(rec(
 PackageName := "Digraphs",
 Subtitle := "Graphs, digraphs, and multidigraphs in GAP",
@@ -568,7 +564,7 @@ PackageDoc := rec(
 ),
 
 Dependencies := rec(
-  GAP := ">=4.11.0",
+  GAP := ">=4.13.0",
   NeededOtherPackages := [["IO", ">=4.5.1"],
                           ["orb", ">=4.8.2"],
                           ["datastructures", ">=0.2.5"]],
@@ -607,26 +603,16 @@ BannerString := Concatenation(
   "-----------------------------------------------------------------------",
   "------\n"),
 
+Extensions := [
+  rec(needed   := [["NautyTracesInterface", ">=0.2"]],
+      filename := "gap/nauty.g")],
+
 AvailabilityTest := function()
-  local digraphs_so;
-
-  if CompareVersionNumbers(GAPInfo.Version, "4.12") then
-    if not IsKernelExtensionAvailable("digraphs") then
-      LogPackageLoadingMessage(PACKAGE_WARNING,
-                              ["the kernel module is not compiled, ",
-                               "the package cannot be loaded."]);
-      return fail;
-    fi;
-  else
-    # TODO this clause can be removed once Digraphs requires GAP>=4.12.1
-    digraphs_so := Filename(DirectoriesPackagePrograms("digraphs"),
-                            "digraphs.so");
-    if (not "digraphs" in SHOW_STAT()) and digraphs_so = fail then
-       LogPackageLoadingMessage(PACKAGE_WARNING,
-                                ["the kernel module is not compiled, ",
-                                 "the package cannot be loaded."]);
-      return fail;
-    fi;
+  if not IsKernelExtensionAvailable("digraphs") then
+    LogPackageLoadingMessage(PACKAGE_WARNING,
+                             ["the kernel module is not compiled, ",
+                              "the package cannot be loaded."]);
+    return fail;
   fi;
   return true;
 end,
@@ -665,10 +651,6 @@ AutoDoc := rec(
             "&Digraphs;", "<Strong>Digraphs</Strong>"),
             "&GAP;", "<Strong>GAP</Strong>")));
 
-if not CompareVersionNumbers(GAPInfo.Version, "4.12") then
-  Unbind(IsKernelExtensionAvailable);
-fi;
-
 MakeReadWriteGlobal("_RecogsFunnyWWWURLFunction");
 MakeReadWriteGlobal("_RecogsFunnyNameFormatterFunction");
 Unbind(_RecogsFunnyWWWURLFunction);

diff --git a/README.md b/README.md
@@ -27,7 +27,7 @@ For questions, remarks, suggestions, and issues please use the
 ## Installation
 
 It is assumed that you have a working copy of [GAP][] with version number
-4.11.0 or higher.  The most up-to-date version of GAP, and instructions on how
+4.13.0 or higher.  The most up-to-date version of GAP, and instructions on how
 to install it, can be obtained from the 
 [main GAP webpage](https://www.gap-system.org).
 

diff --git a/gap/digraph.gi b/gap/digraph.gi
@@ -236,12 +236,13 @@ end);
 InstallMethod(DigraphCons, "for IsMutableDigraph and a record",
 [IsMutableDigraph, IsRecord],
 function(_, record)
-  local D, cmp, labels, i;
+  local D, cmp, labels, i, adj;
 
-  if IsGraph(record) then
+  if DIGRAPHS_IsGrapeGraph(record) then
     # IsGraph is a function not a filter, so we cannot have a separate method
+    adj := ValueGlobal("Adjacency");
     D := DigraphNC(IsMutableDigraph,
-                   List(Vertices(record), x -> Adjacency(record, x)));
+                   List(ValueGlobal("Vertices")(record), x -> adj(record, x)));
     if IsBound(record.names) then
       SetDigraphVertexLabels(D, StructuralCopy(record.names));
     fi;
@@ -382,7 +383,7 @@ InstallMethod(DigraphCons, "for IsImmutableDigraph and a record",
 function(_, record)
   local D;
   D := MakeImmutable(DigraphCons(IsMutableDigraph, record));
-  if IsGraph(record) then
+  if DIGRAPHS_IsGrapeGraph(record) then
     # IsGraph is a function not a filter, so we cannot have a separate method
     # for this.
     if not IsTrivial(record.group) then

diff --git a/gap/isomorph.gi b/gap/isomorph.gi
@@ -130,38 +130,9 @@ end);
 
 BindGlobal("BLISS_DATA_NO_COLORS", D -> BLISS_DATA(D, fail, fail));
 
-if DIGRAPHS_NautyAvailable then
-  BindGlobal("NAUTY_DATA",
-  function(D, colors)
-    local data;
-    if colors <> false then
-      colors := DIGRAPHS_ValidateVertexColouring(DigraphNrVertices(D),
-                                                 colors);
-      colors := NautyColorData(colors);
-    fi;
-    if DigraphHasNoVertices(D) then
-      # This circumvents Issue #17 in NautyTracesInterface, whereby a graph
-      # with 0 vertices causes a seg fault.
-      return [Group(()), ()];
-    fi;
-    data := NautyDense(DigraphSource(D),
-                       DigraphRange(D),
-                       DigraphNrVertices(D),
-                       not IsSymmetricDigraph(D),
-                       colors);
-    if IsEmpty(data[1]) then
-      data[1] := [()];
-    fi;
-    data[1] := Group(data[1]);
-    data[2] := data[2] ^ -1;
-    return data;
-  end);
-
-  BindGlobal("NAUTY_DATA_NO_COLORS", D -> NAUTY_DATA(D, false));
-else
-  BindGlobal("NAUTY_DATA", ReturnFail);
-  BindGlobal("NAUTY_DATA_NO_COLORS", ReturnFail);
-fi;
+# replaced by gap/nauty.g once NautyTracesInterface is loaded
+BindGlobal("NAUTY_DATA", ReturnFail);
+BindGlobal("NAUTY_DATA_NO_COLORS", D -> NAUTY_DATA(D, false));
 
 # Canonical labellings
 

diff --git a/gap/nauty.g b/gap/nauty.g
@@ -0,0 +1,43 @@
+#############################################################################
+##
+##  nauty.g
+##  Copyright (C) 2014-19                                James D. Mitchell
+##                                                          Wilf A. Wilson
+##
+##  Licensing information can be found in the README file of this package.
+##
+#############################################################################
+##
+
+# Package extension, read by GAP once NautyTracesInterface is loaded.
+
+MakeReadWriteGlobal("NAUTY_DATA");
+NAUTY_DATA := function(D, colors)
+  local data;
+  if colors <> false then
+    colors := DIGRAPHS_ValidateVertexColouring(DigraphNrVertices(D),
+                                               colors);
+    colors := NautyColorData(colors);
+  fi;
+  if DigraphHasNoVertices(D) then
+    # This circumvents Issue #17 in NautyTracesInterface, whereby a graph
+    # with 0 vertices causes a seg fault.
+    return [Group(()), ()];
+  fi;
+  data := NautyDense(DigraphSource(D),
+                     DigraphRange(D),
+                     DigraphNrVertices(D),
+                     not IsSymmetricDigraph(D),
+                     colors);
+  if IsEmpty(data[1]) then
+    data[1] := [()];
+  fi;
+  data[1] := Group(data[1]);
+  data[2] := data[2] ^ -1;
+  return data;
+end;
+MakeReadOnlyGlobal("NAUTY_DATA");
+
+MakeReadWriteGlobal("DIGRAPHS_NautyAvailable");
+DIGRAPHS_NautyAvailable := true;
+MakeReadOnlyGlobal("DIGRAPHS_NautyAvailable");
diff --git a/gap/oper.gi b/gap/oper.gi
@@ -2548,7 +2548,7 @@ InstallMethod(DigraphCycleBasis, "for a digraph",
 [IsDigraph],
 function(G)
   local OutNbr, InNbr, n, partialSum, m, visited, unusedEdges, i, c, s, stack,
-    z, u, v, p, B;
+    u, v, p, B;
 
   # Check for loops
   if DigraphHasLoops(G) then
@@ -2631,14 +2631,7 @@ function(G)
   # - unusedEdges : The list of unused edges to be converted to a basis vector
   # - visited : The result of the depth first search above
 
-  # TODO : In the case the Digraph package requires GAP 4.12 or over,
-  # remove the following if statement.
-  if CompareVersionNumbers(GAPInfo.Version, "4.12") then
-    B := List([1 .. c], i -> NewZeroVector(IsGF2VectorRep, GF(2), m));
-  else
-    z := List([1 .. m], i -> Zero(GF(2)));
-    B := List([1 .. c], i -> Vector(GF(2), z));
-  fi;
+  B := List([1 .. c], i -> NewZeroVector(IsGF2VectorRep, GF(2), m));
 
   for i in [1 .. c] do
     u := unusedEdges[i][1];

diff --git a/init.g b/init.g
@@ -8,43 +8,16 @@
 #############################################################################
 ##
 
-# load a method for UserHomeExpand if necessary
-if not IsBound(UserHomeExpand) then
-  BindGlobal("UserHomeExpand", USER_HOME_EXPAND);
-fi;
-
-if CompareVersionNumbers(GAPInfo.Version, "4.12") then
-  if not LoadKernelExtension("digraphs") then
-    Error("failed to load the Digraphs package kernel extension");
-  fi;
-else
-  # TODO this clause can be removed once Digraphs requires GAP>=4.12.1
-  # load kernel function if it is installed:
-  if not IsBound(DIGRAPH_OUT_NBS) and "digraphs" in SHOW_STAT() then
-    # try static module
-    LoadStaticModule("digraphs");
-  fi;
-  if not IsBound(DIGRAPH_OUT_NBS) and
-      Filename(DirectoriesPackagePrograms("digraphs"),
-               "digraphs.so") <> fail then
-    LoadDynamicModule(Filename(DirectoriesPackagePrograms("digraphs"),
-                               "digraphs.so"));
-  fi;
+if not LoadKernelExtension("digraphs") then
+  Error("failed to load the Digraphs package kernel extension");
 fi;
 
 BindGlobal("DIGRAPHS_IsGrapeLoaded",
            {} -> IsPackageMarkedForLoading("grape", "4.8.1"));
 
-# To avoid warnings when GRAPE is not loaded
-if not IsBound(IsGraph) then
-  IsGraph := ReturnFalse;
-fi;
-if not IsBound(Vertices) then
-  DeclareOperation("Vertices", [IsRecord]);
-fi;
-if not IsBound(Adjacency) then
-  Adjacency := IdFunc;
-fi;
+# IsGraph belongs to GRAPE, which need not be loaded
+BindGlobal("DIGRAPHS_IsGrapeGraph",
+           x -> DIGRAPHS_IsGrapeLoaded() and ValueGlobal("IsGraph")(x));
 
 ReadPackage("digraphs", "gap/digraph.gd");
 ReadPackage("digraphs", "gap/digraphs.g");

diff --git a/read.g b/read.g
@@ -20,15 +20,8 @@ function()
   return omit;
 end);
 
-_NautyTracesInterfaceVersion :=
-  First(PackageInfo("digraphs")[1].Dependencies.SuggestedOtherPackages,
-        x -> x[1] = "NautyTracesInterface")[2];
-
-BindGlobal("DIGRAPHS_NautyAvailable",
-  IsPackageMarkedForLoading("NautyTracesInterface",
-                            _NautyTracesInterfaceVersion));
-
-Unbind(_NautyTracesInterfaceVersion);
+# set to true by gap/nauty.g once NautyTracesInterface is loaded
+BindGlobal("DIGRAPHS_NautyAvailable", false);
 
 ReadPackage("digraphs", "gap/utils.gi");
 ReadPackage("digraphs", "gap/digraph.gi");