diff --git a/.gaplint.yml b/.gaplint.yml
index a6e81f9d9..892afe13f 100644
--- a/.gaplint.yml
+++ b/.gaplint.yml
@@ -1,2 +1,3 @@
 disable:
   - align-assignments
+duplicate-function-min-length: 4
diff --git a/doc/digraph.xml b/doc/digraph.xml
index bae318126..d992fbe3e 100644
--- a/doc/digraph.xml
+++ b/doc/digraph.xml
@@ -752,7 +752,7 @@ gap> T := AsSemigroup(IsPartialPermSemigroup,
 gap> Size(T);
 20
 gap> D := GreensDClasses(T);;
-gap> List(D, x -> Size(x));
+gap> List(D, Size);
 [ 6, 12, 2 ]
 ]]></Example>
     </Description>
diff --git a/doc/examples.xml b/doc/examples.xml
index d3c63f92f..f9a2c9c6a 100644
--- a/doc/examples.xml
+++ b/doc/examples.xml
@@ -943,7 +943,7 @@ gap> D := BondyGraph(1);
 gap> IsHamiltonianDigraph(D);
 false
 gap> G := List([1 .. 22], x -> DigraphRemoveVertex(D, x));;
-gap> ForAll(G, x -> IsHamiltonianDigraph(x));
+gap> ForAll(G, IsHamiltonianDigraph);
 true]]></Example>
   </Description>
 </ManSection>
diff --git a/etc/gaplint.sh b/etc/gaplint.sh
index 57c8b27e6..a478f4697 100755
--- a/etc/gaplint.sh
+++ b/etc/gaplint.sh
@@ -1,4 +1,4 @@
 #!/bin/bash
 set -e
 
-gaplint --disable W004 *.g gap/* doc/*.xml tst/testinstall.tst tst/standard/*.tst tst/extreme/*.tst tst/workspaces/*.tst
+gaplint --disable W004 $@ *.g gap/* doc/*.xml tst/testinstall.tst tst/standard/*.tst tst/extreme/*.tst tst/workspaces/*.tst
diff --git a/gap/attr.gi b/gap/attr.gi
index 1f0b2dde0..1d99d2015 100644
--- a/gap/attr.gi
+++ b/gap/attr.gi
@@ -154,15 +154,11 @@ end);
 
 InstallMethod(ArticulationPoints, "for a digraph by out-neighbours",
 [IsDigraphByOutNeighboursRep],
-function(D)
-  return DIGRAPHS_ArticulationPointsBridgesStrongOrientation(D)[2];
-end);
+D -> DIGRAPHS_ArticulationPointsBridgesStrongOrientation(D)[2]);
 
 InstallMethod(Bridges, "for a digraph by out-neighbours",
 [IsDigraphByOutNeighboursRep],
-function(D)
-  return DIGRAPHS_ArticulationPointsBridgesStrongOrientation(D)[3];
-end);
+D -> DIGRAPHS_ArticulationPointsBridgesStrongOrientation(D)[3]);
 
 InstallMethodThatReturnsDigraph(StrongOrientation,
 "for a digraph by out-neighbours",
diff --git a/gap/digraph.gi b/gap/digraph.gi
index e4c0d2704..4516135ab 100644
--- a/gap/digraph.gi
+++ b/gap/digraph.gi
@@ -105,7 +105,7 @@ list -> MakeImmutable(ConvertToMutableDigraphNC(list)));
 
 InstallMethod(DigraphConsNC, "for IsMutableDigraph and a record",
 [IsMutableDigraph, IsRecord],
-function(filt, record)
+function(_, record)
   local required, out, name;
   required := ["DigraphRange", "DigraphSource", "DigraphNrVertices"];
   for name in required do
@@ -123,7 +123,7 @@ end);
 InstallMethod(DigraphConsNC,
 "for IsMutableDigraph and a dense list of out-neighbours",
 [IsMutableDigraph, IsDenseList],
-function(filt, list)
+function(_, list)
   Assert(1, not IsMutable(list));
   return ConvertToMutableDigraphNC(List(list, ShallowCopy));
 end);
@@ -131,11 +131,11 @@ end);
 InstallMethod(DigraphConsNC,
 "for IsMutableDigraph and a dense mutable list of out-neighbours",
 [IsMutableDigraph, IsDenseList and IsMutable],
-{filt, list} -> ConvertToMutableDigraphNC(StructuralCopy(list)));
+{_, list} -> ConvertToMutableDigraphNC(StructuralCopy(list)));
 
 InstallMethod(DigraphConsNC, "for IsImmutableDigraph and a record",
 [IsImmutableDigraph, IsRecord],
-function(filt, record)
+function(_, record)
   local D;
   D := MakeImmutable(DigraphConsNC(IsMutableDigraph, record));
   SetDigraphSource(D, StructuralCopy(record.DigraphSource));
@@ -145,7 +145,7 @@ end);
 
 InstallMethod(DigraphConsNC, "for IsImmutableDigraph and a dense list",
 [IsImmutableDigraph, IsDenseList],
-{filt, list} -> MakeImmutable(DigraphConsNC(IsMutableDigraph, list)));
+{_, list} -> MakeImmutable(DigraphConsNC(IsMutableDigraph, list)));
 
 InstallMethod(DigraphNC, "for a function and a dense list",
 [IsFunction, IsDenseList], DigraphConsNC);
@@ -235,7 +235,7 @@ end);
 
 InstallMethod(DigraphCons, "for IsMutableDigraph and a record",
 [IsMutableDigraph, IsRecord],
-function(filt, record)
+function(_, record)
   local D, cmp, labels, i;
 
   if IsGraph(record) then
@@ -287,9 +287,9 @@ function(filt, record)
     record.DigraphNrVertices := Length(record.DigraphVertices);
   fi;
 
-  if not ForAll(record.DigraphSource, x -> cmp(x)) then
+  if not ForAll(record.DigraphSource, cmp) then
     ErrorNoReturn("the record component 'DigraphSource' is invalid,");
-  elif not ForAll(record.DigraphRange, x -> cmp(x)) then
+  elif not ForAll(record.DigraphRange, cmp) then
     ErrorNoReturn("the record component 'DigraphRange' is invalid,");
   fi;
 
@@ -321,7 +321,7 @@ end);
 InstallMethod(DigraphCons,
 "for IsMutableDigraph and a dense list of out-neighbours",
 [IsMutableDigraph, IsDenseList],
-function(filt, list)
+function(_, list)
   local sublist, v;
   for sublist in list do
     if not IsHomogeneousList(sublist) then
@@ -341,7 +341,7 @@ end);
 
 InstallMethod(DigraphCons, "for IsMutableDigraph, a list, and function",
 [IsMutableDigraph, IsList, IsFunction],
-function(filt, list, func)
+function(_, list, func)
   local N, out, x, i, j;
   N    := Size(list);  # number of vertices
   out := List([1 .. N], x -> []);
@@ -359,7 +359,7 @@ end);
 InstallMethod(DigraphCons,
 "for IsMutableDigraph, a number of vertices, source, and range",
 [IsMutableDigraph, IsInt, IsList, IsList],
-function(filt, N, src, ran)
+function(_, N, src, ran)
   return DigraphCons(IsMutableDigraph, rec(DigraphNrVertices := N,
                                            DigraphSource     := src,
                                            DigraphRange      := ran));
@@ -368,7 +368,7 @@ end);
 InstallMethod(DigraphCons,
 "for IsMutableDigraph, a list of vertices, source, and range",
 [IsMutableDigraph, IsList, IsList, IsList],
-function(filt, domain, src, ran)
+function(_, domain, src, ran)
   local D;
   D := DigraphCons(IsMutableDigraph, rec(DigraphVertices := domain,
                                          DigraphSource   := src,
@@ -379,7 +379,7 @@ end);
 
 InstallMethod(DigraphCons, "for IsImmutableDigraph and a record",
 [IsImmutableDigraph, IsRecord],
-function(filt, record)
+function(_, record)
   local D;
   D := MakeImmutable(DigraphCons(IsMutableDigraph, record));
   if IsGraph(record) then
@@ -400,11 +400,11 @@ end);
 InstallMethod(DigraphCons,
 "for IsImmutableDigraph and a dense list of out-neighbours",
 [IsImmutableDigraph, IsDenseList],
-{filt, list} -> MakeImmutable(DigraphCons(IsMutableDigraph, list)));
+{_, list} -> MakeImmutable(DigraphCons(IsMutableDigraph, list)));
 
 InstallMethod(DigraphCons, "for IsImmutableDigraph, a list, and function",
 [IsImmutableDigraph, IsList, IsFunction],
-function(filt, list, func)
+function(_, list, func)
   local D;
   D := MakeImmutable(DigraphCons(IsMutableDigraph, list, func));
   SetDigraphAdjacencyFunction(D, {u, v} -> func(list[u], list[v]));
@@ -416,16 +416,14 @@ end);
 InstallMethod(DigraphCons,
 "for IsImmutableDigraph, a number of vertices, source, and range",
 [IsImmutableDigraph, IsInt, IsList, IsList],
-function(filt, N, src, ran)
-  return MakeImmutable(DigraphCons(IsMutableDigraph, N, src, ran));
-end);
+{_, N, src, ran}
+-> MakeImmutable(DigraphCons(IsMutableDigraph, N, src, ran)));
 
 InstallMethod(DigraphCons,
 "for IsImmutableDigraph, a list of vertices, source, and range",
 [IsImmutableDigraph, IsList, IsList, IsList],
-function(filt, domain, src, ran)
-  return MakeImmutable(DigraphCons(IsMutableDigraph, domain, src, ran));
-end);
+{_, domain, src, ran} ->
+MakeImmutable(DigraphCons(IsMutableDigraph, domain, src, ran)));
 
 InstallMethod(Digraph, "for a filter and a record", [IsFunction, IsRecord],
 DigraphCons);
@@ -744,7 +742,7 @@ function(D)
     fi;
   od;
 
-  lengths := List(strings, x -> Length(x));
+  lengths := List(strings, Length);
   return strings[Position(lengths, Minimum(lengths))];
 end);
 
@@ -763,7 +761,7 @@ InstallMethod(\<, "for two digraphs", [IsDigraph, IsDigraph], DIGRAPH_LT);
 InstallMethod(DigraphByAdjacencyMatrixConsNC,
 "for IsMutableDigraph and a homogeneous list",
 [IsMutableDigraph, IsHomogeneousList],
-function(filt, mat)
+function(_, mat)
   local add_edge, n, list, i, j;
 
   if IsInt(mat[1][1]) then
@@ -795,7 +793,7 @@ end);
 InstallMethod(DigraphByAdjacencyMatrixCons,
 "for IsMutableDigraph and a homogeneous list",
 [IsMutableDigraph, IsHomogeneousList],
-function(filt, mat)
+function(_, mat)
   local n, i, j;
   n := Length(mat);
   if not IsRectangularTable(mat) or Length(mat[1]) <> n then
@@ -820,12 +818,12 @@ InstallMethod(DigraphByAdjacencyMatrixCons,
 InstallMethod(DigraphByAdjacencyMatrixConsNC,
 "for IsMutableDigraph and an empty list",
 [IsMutableDigraph, IsList and IsEmpty],
-{filt, dummy} -> EmptyDigraph(IsMutableDigraph, 0));
+{_, dummy} -> EmptyDigraph(IsMutableDigraph, 0));
 
 InstallMethod(DigraphByAdjacencyMatrixCons,
 "for IsImmutableDigraph and a homogeneous list",
 [IsImmutableDigraph, IsHomogeneousList],
-function(filt, mat)
+function(_, mat)
   local D;
   D := MakeImmutable(DigraphByAdjacencyMatrixCons(IsMutableDigraph, mat));
   if IsEmpty(mat) or IsInt(mat[1][1]) then
@@ -848,7 +846,7 @@ mat -> DigraphByAdjacencyMatrixCons(IsImmutableDigraph, mat));
 InstallMethod(DigraphByEdgesCons,
 "for IsMutableDigraph, a list, and an integer",
 [IsMutableDigraph, IsList, IsInt],
-function(filt, edges, n)
+function(_, edges, n)
   local list, edge;
   if IsEmpty(edges) then
     return NullDigraph(IsMutableDigraph, n);
@@ -870,7 +868,7 @@ end);
 
 InstallMethod(DigraphByEdgesCons, "for IsMutableDigraph and a list",
 [IsMutableDigraph, IsList],
-function(filt, edges)
+function(_, edges)
   local n;
   if IsEmpty(edges) then
     n := 0;
@@ -882,7 +880,7 @@ end);
 
 InstallMethod(DigraphByEdgesCons, "for an ImmutableDigraph and a list",
 [IsImmutableDigraph, IsList],
-function(filt, edges)
+function(_, edges)
   local D;
   D := MakeImmutable(DigraphByEdges(IsMutableDigraph, edges));
   SetDigraphEdges(D, edges);
@@ -893,7 +891,7 @@ end);
 InstallMethod(DigraphByEdgesCons,
 "for IsImmutableDigraph, a list, and an integer",
 [IsImmutableDigraph, IsList, IsInt],
-function(filt, edges, n)
+function(_, edges, n)
   local D;
   D := MakeImmutable(DigraphByEdges(IsMutableDigraph, edges, n));
   SetDigraphEdges(D, edges);
@@ -916,7 +914,7 @@ InstallMethod(DigraphByEdges, "for a function and a list",
 
 InstallMethod(DigraphByInNeighboursCons, "for IsMutableDigraph, and a list",
 [IsMutableDigraph, IsList],
-function(filt, list)
+function(_, list)
   local n, x;
   n := Length(list);  # number of vertices
   for x in list do
@@ -930,7 +928,7 @@ end);
 
 InstallMethod(DigraphByInNeighboursCons, "for IsImmutableDigraph and a list",
 [IsImmutableDigraph, IsList],
-function(filt, list)
+function(_, list)
   local D;
   D := MakeImmutable(DigraphByInNeighboursCons(IsMutableDigraph, list));
   SetInNeighbours(D, list);
@@ -939,11 +937,11 @@ end);
 
 InstallMethod(DigraphByInNeighboursConsNC, "for IsMutableDigraph and a list",
 [IsMutableDigraph, IsList],
-{filt, list} -> DigraphNC(IsMutableDigraph, DIGRAPH_IN_OUT_NBS(list)));
+{_, list} -> DigraphNC(IsMutableDigraph, DIGRAPH_IN_OUT_NBS(list)));
 
 InstallMethod(DigraphByInNeighboursConsNC, "for IsImmutableDigraph and a list",
 [IsImmutableDigraph, IsList],
-function(filt, list)
+function(_, list)
   local D;
   D := MakeImmutable(DigraphByInNeighboursConsNC(IsMutableDigraph, list));
   SetInNeighbours(D, list);
@@ -963,7 +961,7 @@ DigraphByInNeighboursCons);
 
 InstallMethod(AsDigraphCons, "for IsMutableDigraph and a binary relation",
 [IsMutableDigraph, IsBinaryRelation],
-function(filt, rel)
+function(_, rel)
   local dom, list, i;
   dom := GeneratorsOfDomain(UnderlyingDomainOfBinaryRelation(rel));
   if not IsRange(dom) or dom[1] <> 1 then
@@ -979,7 +977,7 @@ end);
 
 InstallMethod(AsDigraphCons, "for IsImmutableDigraph and a binary relation",
 [IsImmutableDigraph, IsBinaryRelation],
-function(filt, rel)
+function(_, rel)
   local D;
   D := MakeImmutable(AsDigraph(IsMutableDigraph, rel));
   SetIsMultiDigraph(D, false);
@@ -1007,7 +1005,7 @@ InstallMethod(AsDigraph, "for a function and a binary relation",
 InstallMethod(AsDigraphCons,
 "for IsMutableDigraph, a transformation, and an integer",
 [IsMutableDigraph, IsTransformation, IsInt],
-function(filt, f, n)
+function(_, f, n)
   local list, x, i;
   if n < 0 then
     ErrorNoReturn("the 2nd argument <n> should be a non-negative integer,");
@@ -1027,7 +1025,7 @@ end);
 InstallMethod(AsDigraphCons,
 "for IsImmutableDigraph, a transformation, and an integer",
 [IsImmutableDigraph, IsTransformation, IsInt],
-function(filt, f, n)
+function(_, f, n)
   local D;
   D := AsDigraph(IsMutableDigraph, f, n);
   if D <> fail then
@@ -1071,7 +1069,7 @@ p -> AsDigraph(AsTransformation(p)));
 InstallMethod(AsDigraphCons,
 "for IsMutableDigraph, a partial perm, and an integer",
 [IsMutableDigraph, IsPartialPerm, IsInt],
-function(filt, f, n)
+function(_, f, n)
   local list, x, i;
   if n < 0 then
     ErrorNoReturn("the 2nd argument <n> should be a non-negative integer,");
@@ -1094,7 +1092,7 @@ end);
 InstallMethod(AsDigraphCons,
 "for IsImmutableDigraph, a partial perm, and an integer",
 [IsImmutableDigraph, IsPartialPerm, IsInt],
-function(filt, f, n)
+function(_, f, n)
   local D;
   D := AsDigraph(IsMutableDigraph, f, n);
   if D <> fail then
@@ -1220,7 +1218,7 @@ function(filt, digraph, gps, homs)
       ErrorNoReturn("the second argument must be a join semilattice ",
                     "digraph or a meet semilattice digraph,");
     fi;
-  elif not ForAll(gps, x -> IsGroup(x)) then
+  elif not ForAll(gps, IsGroup) then
     ErrorNoReturn("the third argument must be a list of groups,");
   elif not Length(gps) = DigraphNrVertices(digraph) then
     ErrorNoReturn("the third argument must have length equal to the number ",
@@ -1344,70 +1342,63 @@ end);
 
 InstallMethod(RandomDigraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsInt],
-function(filt, n)
-  return RandomDigraphCons(IsMutableDigraph, n, Float(Random([0 .. n])) / n);
-end);
+{_, n}
+-> RandomDigraphCons(IsMutableDigraph, n, Float(Random([0 .. n])) / n));
 
 InstallMethod(RandomDigraphCons, "for IsMutableDigraph and an integer",
 [IsImmutableDigraph, IsInt],
-function(filt, n)
-  return RandomDigraphCons(IsImmutableDigraph, n, Float(Random([0 .. n])) / n);
-end);
+{_, n}
+-> RandomDigraphCons(IsImmutableDigraph, n, Float(Random([0 .. n])) / n));
 
 InstallMethod(RandomDigraphCons, "for IsHamiltonianDigraph and an integer",
 [IsHamiltonianDigraph, IsInt],
-function(filt, n)
-  return RandomDigraphCons(IsHamiltonianDigraph, n, Float(Random([0 .. n])) / n);
-end);
+{_, n}
+-> RandomDigraphCons(IsHamiltonianDigraph, n, Float(Random([0 .. n])) / n));
 
 InstallMethod(RandomDigraphCons, "for IsEulerianDigraph and an integer",
 [IsEulerianDigraph, IsInt],
-function(filt, n)
-  return RandomDigraphCons(IsEulerianDigraph, n, Float(Random([0 .. n])) / n);
-end);
+{_, n}
+-> RandomDigraphCons(IsEulerianDigraph, n, Float(Random([0 .. n])) / n));
 
 InstallMethod(RandomDigraphCons, "for IsConnectedDigraph and an integer",
 [IsConnectedDigraph, IsInt],
-function(filt, n)
-  return RandomDigraphCons(IsConnectedDigraph, n, Float(Random([0 .. n])) / n);
-end);
+{_, n}
+-> RandomDigraphCons(IsConnectedDigraph, n, Float(Random([0 .. n])) / n));
 
 InstallMethod(RandomDigraphCons, "for IsAcyclicDigraph and an integer",
 [IsAcyclicDigraph, IsInt],
-function(filt, n)
-  return RandomDigraphCons(IsAcyclicDigraph, n, Float(Random([0 .. n])) / n);
-end);
+{_, n}
+-> RandomDigraphCons(IsAcyclicDigraph, n, Float(Random([0 .. n])) / n));
 
 InstallMethod(RandomDigraphCons, "for IsSymmetricDigraph and an integer",
 [IsSymmetricDigraph, IsInt],
-function(filt, n)
-  return RandomDigraphCons(IsSymmetricDigraph, n, Float(Random([0 .. n])) / n);
-end);
+{_, n}
+-> RandomDigraphCons(IsSymmetricDigraph, n, Float(Random([0 .. n])) / n));
 
 InstallMethod(RandomDigraphCons,
 "for IsMutableDigraph, an integer, and a rational",
 [IsMutableDigraph, IsInt, IsRat],
-{filt, n, p} -> RandomDigraphCons(IsMutableDigraph, n, Float(p)));
+{_, n, p} -> RandomDigraphCons(IsMutableDigraph, n, Float(p)));
 
 InstallMethod(RandomDigraphCons,
 "for IsImmutableDigraph, an integer, and a rational",
 [IsImmutableDigraph, IsInt, IsRat],
-{filt, n, p} -> RandomDigraphCons(IsImmutableDigraph, n, Float(p)));
+{_, n, p} -> RandomDigraphCons(IsImmutableDigraph, n, Float(p)));
 
 InstallMethod(RandomDigraphCons,
 "for IsHamiltonianDigraph, an integer, and a rational",
 [IsHamiltonianDigraph, IsInt, IsRat],
-{filt, n, p} -> RandomDigraphCons(IsHamiltonianDigraph, n, Float(p)));
+{_, n, p} -> RandomDigraphCons(IsHamiltonianDigraph, n, Float(p)));
 
 InstallMethod(RandomDigraphCons,
 "for IsEulerianDigraph, an integer, and a rational",
 [IsEulerianDigraph, IsInt, IsRat],
-{filt, n, p} -> RandomDigraphCons(IsEulerianDigraph, n, Float(p)));
+{_, n, p} -> RandomDigraphCons(IsEulerianDigraph, n, Float(p)));
 
 InstallMethod(RandomDigraphCons,
 "for IsConnectedDigraph, an integer, and a rational",
 [IsConnectedDigraph, IsInt, IsRat],
-{filt, n, p} -> RandomDigraphCons(IsConnectedDigraph, n, Float(p)));
+{_, n, p} -> RandomDigraphCons(IsConnectedDigraph, n, Float(p)));
 
 InstallMethod(RandomDigraphCons,
 "for IsStronglyConnectedDigraph, an integer, and a rational",
@@ -1417,17 +1408,17 @@ InstallMethod(RandomDigraphCons,
 InstallMethod(RandomDigraphCons,
 "for IsAcyclicDigraph, an integer, and a rational",
 [IsAcyclicDigraph, IsInt, IsRat],
-{filt, n, p} -> RandomDigraphCons(IsAcyclicDigraph, n, Float(p)));
+{_, n, p} -> RandomDigraphCons(IsAcyclicDigraph, n, Float(p)));
 
 InstallMethod(RandomDigraphCons,
 "for IsSymmetricDigraph, an integer, and a rational",
 [IsSymmetricDigraph, IsInt, IsRat],
-{filt, n, p} -> RandomDigraphCons(IsSymmetricDigraph, n, Float(p)));
+{_, n, p} -> RandomDigraphCons(IsSymmetricDigraph, n, Float(p)));
 
 InstallMethod(RandomDigraphCons,
 "for IsMutableDigraph, a positive integer, and a float",
 [IsMutableDigraph, IsPosInt, IsFloat],
-function(filt, n, p)
+function(_, n, p)
   if p < 0.0 or 1.0 < p then
     ErrorNoReturn("the 2nd argument <p> must be between 0 and 1,");
   fi;
@@ -1459,7 +1450,7 @@ end);
 InstallMethod(RandomDigraphCons,
 "for IsHamiltonianDigraph, a positive integer, and a float",
 [IsHamiltonianDigraph, IsPosInt, IsFloat],
-function(filt, n, p)
+function(_, n, p)
     local adjacencyList, vertices, i, startVertex, hamiltonianCycle, x, j;
 
     adjacencyList := EmptyPlist(n);
@@ -1506,7 +1497,7 @@ end);
 InstallMethod(RandomDigraphCons,
 "for IsEulerianDigraph, a positive integer, and a float",
 [IsEulerianDigraph, IsPosInt, IsFloat],
-function(filt, n, p)
+function(_, n, p)
     local adjacencyList, vertices, probability, startVertex, circuitVertex, i,
     continueCircuit, verticesToConsider, connectedVertices, verticesToCheck;
 
@@ -1605,7 +1596,7 @@ end);
 InstallMethod(RandomDigraphCons,
 "for IsConnectedDigraph, a positive integer, and a float",
 [IsConnectedDigraph, IsPosInt, IsFloat],
-function(filt, n, p)
+function(_, n, p)
     local adjacencyList, vertices, startVertex, tree, x, i, j;
 
     adjacencyList := EmptyPlist(n);
@@ -1678,7 +1669,7 @@ end);
 InstallMethod(RandomDigraphCons,
 "for IsAcyclicDigraph, a positive integer, and a float",
 [IsAcyclicDigraph, IsPosInt, IsFloat],
-function(filt, n, p)
+function(_, n, p)
     local adjacencyList, vertices, probability, i, j;
 
     adjacencyList := EmptyPlist(n);
@@ -1711,7 +1702,7 @@ end);
 InstallMethod(RandomDigraphCons,
 "for IsSymmetricDigraph, a positive integer, and a float",
 [IsSymmetricDigraph, IsPosInt, IsFloat],
-function(filt, n, p)
+function(_, n, p)
     local adjacencyList, vertices, probability, i, j;
 
     adjacencyList := EmptyPlist(n);
@@ -1744,7 +1735,7 @@ end);
 InstallMethod(RandomDigraphCons,
 "for IsImmutableDigraph, a positive integer, and a float",
 [IsImmutableDigraph, IsPosInt, IsFloat],
-function(filt, n, p)
+function(_, n, p)
   local D;
   D := MakeImmutable(RandomDigraphCons(IsMutableDigraph, n, p));
   SetIsMultiDigraph(D, false);
@@ -1777,7 +1768,7 @@ InstallMethod(RandomMultiDigraph, "for two pos ints", [IsPosInt, IsPosInt],
 
 InstallMethod(RandomTournamentCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsInt],
-function(filt, n)
+function(_, n)
   local choice, nodes, list, v, w;
   if n < 0 then
     ErrorNoReturn("the argument <n> must be a non-negative integer,");
@@ -1801,7 +1792,7 @@ end);
 
 InstallMethod(RandomTournamentCons, "for IsImmutableDigraph and an integer",
 [IsImmutableDigraph, IsInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(RandomTournamentCons(IsMutableDigraph, n));
   SetIsTournament(D, true);
@@ -1821,7 +1812,7 @@ InstallMethod(RandomTournament, "for a func and an integer",
 
 InstallMethod(RandomLatticeCons, "for IsMutableDigraph and a pos int",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local fam, rand_blist;
 
   fam := [BlistList([1 .. n], [])];
@@ -1836,7 +1827,7 @@ end);
 
 InstallMethod(RandomLatticeCons, "for IsImmutableDigraph and a pos int",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(RandomLatticeCons(IsMutableDigraph, n));
   SetIsLatticeDigraph(D, true);
diff --git a/gap/examples.gi b/gap/examples.gi
index 9db299b0e..a5d0e4be4 100644
--- a/gap/examples.gi
+++ b/gap/examples.gi
@@ -13,7 +13,7 @@
 
 InstallMethod(EmptyDigraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsInt],
-function(filt, n)
+function(_, n)
   if n < 0 then
     ErrorNoReturn("the argument <n> must be a non-negative integer,");
   fi;
@@ -22,7 +22,7 @@ end);
 
 InstallMethod(EmptyDigraphCons, "for IsImmutableDigraph and an integer",
 [IsImmutableDigraph, IsInt],
-function(filt, n)
+function(_, n)
   local D;
   if n < 0 then
     ErrorNoReturn("the argument <n> must be a non-negative integer,");
@@ -43,7 +43,7 @@ InstallMethod(EmptyDigraph, "for a function and an integer",
 InstallMethod(CompleteBipartiteDigraphCons,
 "for IsMutableDigraph and two positive integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local src, ran, count, k, i, j;
   src := EmptyPlist(2 * m * n);
   ran := EmptyPlist(2 * m * n);
@@ -66,7 +66,7 @@ end);
 InstallMethod(CompleteBipartiteDigraphCons,
 "for IsImmutableDigraph and two positive integers",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local D, aut;
   D := MakeImmutable(CompleteBipartiteDigraph(IsMutableDigraph, m, n));
   SetIsSymmetricDigraph(D, true);
@@ -98,7 +98,7 @@ CompleteBipartiteDigraphCons);
 InstallMethod(CompleteMultipartiteDigraphCons,
 "for IsMutableDigraph and a list",
 [IsMutableDigraph, IsList],
-function(filt, list)
+function(_, list)
   local M, N, out, start, next, i, v;
   if not ForAll(list, IsPosInt) then
     ErrorNoReturn("the argument <list> must be a list of positive ",
@@ -127,7 +127,7 @@ end);
 InstallMethod(CompleteMultipartiteDigraphCons,
 "for IsImmutableDigraph and a list",
 [IsImmutableDigraph, IsList],
-function(filt, list)
+function(_, list)
   local D;
   D := MakeImmutable(CompleteMultipartiteDigraph(IsMutableDigraph, list));
   SetIsEmptyDigraph(D, Length(list) <= 1);
@@ -148,7 +148,7 @@ InstallMethod(CompleteMultipartiteDigraph, "for a function and a list",
 
 InstallMethod(ChainDigraphCons, "for IsMutableDigraph and a positive integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local list, i;
   list := EmptyPlist(n);
   for i in [1 .. n - 1] do
@@ -161,7 +161,7 @@ end);
 InstallMethod(ChainDigraphCons,
 "for IsImmutableDigraph and a positive integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(ChainDigraphCons(IsMutableDigraph, n));
   SetIsChainDigraph(D, true);
@@ -186,7 +186,7 @@ n -> ChainDigraphCons(IsImmutableDigraph, n));
 
 InstallMethod(CompleteDigraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsInt],
-function(filt, n)
+function(_, n)
   local verts, out, i;
   if n < 0 then
     ErrorNoReturn("the argument <n> must be a non-negative integer,");
@@ -203,7 +203,7 @@ end);
 
 InstallMethod(CompleteDigraphCons, "for IsImmutableDigraph and an integer",
 [IsImmutableDigraph, IsInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(CompleteDigraphCons(IsMutableDigraph, n));
   SetIsEmptyDigraph(D, n <= 1);
@@ -227,7 +227,7 @@ n -> CompleteDigraphCons(IsImmutableDigraph, n));
 
 InstallMethod(CycleDigraphCons, "for IsMutableDigraph and a positive integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local list, i;
   list := EmptyPlist(n);
   for i in [1 .. n - 1] do
@@ -240,7 +240,7 @@ end);
 InstallMethod(CycleDigraphCons,
 "for IsImmutableDigraph and a positive integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(CycleDigraphCons(IsMutableDigraph, n));
   SetIsAcyclicDigraph(D, false);
@@ -268,7 +268,7 @@ n -> CycleDigraphCons(IsImmutableDigraph, n));
 InstallMethod(JohnsonDigraphCons,
 "for IsMutableDigraph and two integers",
 [IsMutableDigraph, IsInt, IsInt],
-function(filt, n, k)
+function(_, n, k)
   if n < 0 or k < 0 then
     ErrorNoReturn("the arguments <n> and <k> must be ",
                   "non-negative integers,");
@@ -281,7 +281,7 @@ end);
 InstallMethod(JohnsonDigraphCons,
 "for IsImmutableDigraph, integer, integer",
 [IsImmutableDigraph, IsInt, IsInt],
-function(filt, n, k)
+function(_, n, k)
   local D;
   D := MakeImmutable(JohnsonDigraphCons(IsMutableDigraph, n, k));
   SetIsMultiDigraph(D, false);
@@ -297,7 +297,7 @@ InstallMethod(JohnsonDigraph, "for integer, integer", [IsInt, IsInt],
 {n, k} -> JohnsonDigraphCons(IsImmutableDigraph, n, k));
 
 InstallMethod(PetersenGraphCons, "for IsMutableDigraph", [IsMutableDigraph],
-function(filt)
+function(_)
   local mat;
   mat := [[0, 1, 0, 0, 1, 1, 0, 0, 0, 0],
           [1, 0, 1, 0, 0, 0, 1, 0, 0, 0],
@@ -315,7 +315,7 @@ end);
 
 InstallMethod(PetersenGraphCons, "for IsImmutableDigraph",
 [IsImmutableDigraph],
-filt -> MakeImmutable(PetersenGraphCons(IsMutableDigraph)));
+_ -> MakeImmutable(PetersenGraphCons(IsMutableDigraph)));
 
 InstallMethod(PetersenGraph, "for a function", [IsFunction],
 PetersenGraphCons);
@@ -352,7 +352,7 @@ end);
 InstallMethod(GeneralisedPetersenGraphCons,
 "for IsImmutableDigraph, positive integer, int",
 [IsImmutableDigraph, IsPosInt, IsInt],
-function(filt, n, k)
+function(_, n, k)
   local D;
   D := MakeImmutable(GeneralisedPetersenGraphCons(IsMutableDigraph, n, k));
   SetIsMultiDigraph(D, false);
@@ -371,7 +371,7 @@ InstallMethod(GeneralisedPetersenGraph, "for a positive integer and integer",
 InstallMethod(LollipopGraphCons,
 "for IsMutableDigraph and two positive integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local D;
   D := DigraphDisjointUnion(CompleteDigraph(IsMutableDigraph, m),
   DigraphSymmetricClosure(ChainDigraph(IsMutableDigraph, n)));
@@ -382,7 +382,7 @@ end);
 InstallMethod(LollipopGraphCons,
 "for IsImmutableDigraph and two positive integers",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local D;
   D := MakeImmutable(LollipopGraphCons(IsMutableDigraph, m, n));
   SetIsMultiDigraph(D, false);
@@ -412,7 +412,7 @@ InstallMethod(LollipopGraph, "for a function and two pos int",
 InstallMethod(SquareGridGraphCons,
 "for IsMutableDigraph and two positive integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-function(filt, n, k)
+function(_, n, k)
   local D1, D2;
   D1 := DigraphSymmetricClosure(ChainDigraph(IsMutableDigraph, n));
   D2 := DigraphSymmetricClosure(ChainDigraph(IsMutableDigraph, k));
@@ -422,7 +422,7 @@ end);
 InstallMethod(SquareGridGraphCons,
 "for IsImmutableDigraph and two positive integers",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, n, k)
+function(_, n, k)
   local D;
   D := MakeImmutable(SquareGridGraphCons(IsMutableDigraph, n, k));
   SetIsMultiDigraph(D, false);
@@ -447,7 +447,7 @@ InstallMethod(SquareGridGraph, "for two integers", [IsPosInt, IsPosInt],
 InstallMethod(TriangularGridGraphCons,
 "for IsMutableDigraph and two integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-function(filt, n, k)
+function(_, n, k)
   local D, a, b, i, j;
   D := SquareGridGraph(IsMutableDigraph, n, k);
   for i in [1 .. (k - 1)] do
@@ -464,7 +464,7 @@ end);
 InstallMethod(TriangularGridGraphCons,
 "for IsImmutableDigraph and two positive integers",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, n, k)
+function(_, n, k)
   local D;
   D := MakeImmutable(TriangularGridGraphCons(IsMutableDigraph, n, k));
   SetIsMultiDigraph(D, false);
@@ -486,7 +486,7 @@ InstallMethod(TriangularGridGraph, "for two positive integers",
 
 InstallMethod(StarGraphCons, "for IsMutableDigraph and a positive integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, k)
+function(_, k)
   if k = 1 then
     return EmptyDigraph(IsMutable, 1);
   fi;
@@ -503,7 +503,7 @@ InstallMethod(StarGraph, "for integer", [IsPosInt],
 InstallMethod(StarGraphCons,
 "for IsImmutableDigraph and a positive integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, k)
+function(_, k)
   local D;
   D := MakeImmutable(StarGraph(IsMutableDigraph, k));
   SetIsMultiDigraph(D, false);
@@ -515,7 +515,7 @@ end);
 InstallMethod(KingsGraphCons,
 "for IsMutableDigraph and two positive integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-function(filt, n, k)
+function(_, n, k)
   local D, a, b, i, j;
   D := TriangularGridGraph(IsMutableDigraph, n, k);
   for i in [1 .. (k - 1)] do
@@ -532,7 +532,7 @@ end);
 InstallMethod(KingsGraphCons,
 "for IsImmutableDigraph and two positive integers",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, n, k)
+function(_, n, k)
   local D;
   D := MakeImmutable(KingsGraphCons(IsMutableDigraph, n, k));
   SetIsMultiDigraph(D, false);
@@ -555,7 +555,7 @@ InstallMethod(KingsGraph, "two positive integers",
 InstallMethod(QueensGraphCons,
 "for IsMutableDigraph and two integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local D1, D2, labels;
   D1 := RooksGraphCons(IsMutableDigraph, m, n);
   D2 := BishopsGraphCons(IsMutableDigraph, m, n);
@@ -568,7 +568,7 @@ end);
 InstallMethod(QueensGraphCons,
 "for IsImmutableDigraph and two positive integers",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local D;
   D := MakeImmutable(QueensGraphCons(IsMutableDigraph, m, n));
   SetIsMultiDigraph(D, false);
@@ -589,7 +589,7 @@ InstallMethod(QueensGraph, "for two positive integers",
 InstallMethod(RooksGraphCons,
 "for IsMutableDigraph and two positive integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local D1, D2;
   D1 := CompleteDigraph(IsMutableDigraph, m);
   D2 := CompleteDigraph(n);
@@ -599,7 +599,7 @@ end);
 InstallMethod(RooksGraphCons,
 "for IsImmutableDigraph and two positive integers",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local D;
   D := MakeImmutable(RooksGraphCons(IsMutableDigraph, m, n));
   SetIsMultiDigraph(D, false);
@@ -622,7 +622,7 @@ InstallMethod(RooksGraph, "for two positive integers",
 InstallMethod(BishopsGraphCons,
 "for IsMutableDigraph, a string and two positive integers",
 [IsMutableDigraph, IsString, IsPosInt, IsPosInt],
-function(filt, color, m, n)
+function(_, color, m, n)
   local both, dark, nr, D1, D2, upL, inc, step, labels, v, not_final_row, i, j,
         is_dark_square, range;
 
@@ -705,7 +705,7 @@ end);
 InstallMethod(BishopsGraphCons,
 "for IsImmutableDigraph, a string and two positive integers",
 [IsImmutableDigraph, IsString, IsPosInt, IsPosInt],
-function(filt, color, m, n)
+function(_, color, m, n)
   local D;
   D := MakeImmutable(BishopsGraphCons(IsMutableDigraph, color, m, n));
   SetIsMultiDigraph(D, false);
@@ -726,12 +726,12 @@ InstallMethod(BishopsGraph, "for a string and two positive integers",
 InstallMethod(BishopsGraphCons,
 "for IsMutableDigraph and two positive integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-{filt, m, n} -> BishopsGraphCons(IsMutableDigraph, "both", m, n));
+{_, m, n} -> BishopsGraphCons(IsMutableDigraph, "both", m, n));
 
 InstallMethod(BishopsGraphCons,
 "for IsImmutableDigraph and two positive integers",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local D;
   D := MakeImmutable(BishopsGraphCons(IsMutableDigraph, "both", m, n));
   SetIsMultiDigraph(D, false);
@@ -752,7 +752,7 @@ InstallMethod(BishopsGraph, "for two positive integers",
 InstallMethod(KnightsGraphCons,
 "for IsMutableDigraph and two positive integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local D, moves, labels, v, r, s, range, j, i, move;
 
   D := EmptyDigraph(IsMutableDigraph, m * n);
@@ -781,7 +781,7 @@ end);
 InstallMethod(KnightsGraphCons,
 "for IsImmutableDigraph and two positive integers",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local D;
   D := MakeImmutable(KnightsGraphCons(IsMutableDigraph, m, n));
   SetIsMultiDigraph(D, false);
@@ -800,7 +800,7 @@ InstallMethod(KnightsGraph, "for two positive integers", [IsPosInt, IsPosInt],
 InstallMethod(HaarGraphCons,
 "for IsMutableDigraph and a positive integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local m, binaryList, D, i, j;
   m := Log(n, 2) + 1;
   binaryList := DIGRAPHS_BlistNumber(n + 1, m);
@@ -820,7 +820,7 @@ end);
 InstallMethod(HaarGraphCons,
 "for IsImmutableDigraph and a positive integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(HaarGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -841,7 +841,7 @@ InstallMethod(HaarGraph, "for a positive integer", [IsPosInt],
 InstallMethod(BananaTreeCons,
 "for IsMutableDigraph and two positive integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local D, j, list;
   if n = 1 then
     ErrorNoReturn("The second argument must be an integer",
@@ -859,7 +859,7 @@ end);
 InstallMethod(BananaTreeCons,
 "for IsImmutableDigraph and two positive integers",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local D;
   D := MakeImmutable(BananaTreeCons(IsMutableDigraph, m, n));
   SetIsMultiDigraph(D, false);
@@ -879,7 +879,7 @@ InstallMethod(BananaTree, "for a function and two positive integers",
 InstallMethod(TadpoleGraphCons,
 "for IsMutableDigraph and two positive integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local tail, graph;
   if m < 3 then
     ErrorNoReturn("the first argument <m> must be an integer greater than 2");
@@ -901,7 +901,7 @@ InstallMethod(TadpoleGraph, "for two positive integers", [IsPosInt, IsPosInt],
 InstallMethod(TadpoleGraphCons,
 "for IsImmutableDigraph and two positive integers",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local D;
   D := MakeImmutable(TadpoleGraph(IsMutableDigraph, m, n));
   SetIsMultiDigraph(D, false);
@@ -923,7 +923,7 @@ m -> BookGraphCons(IsImmutableDigraph, m));
 InstallMethod(BookGraphCons,
 "for IsImmutableDigraph and a positive integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, m)
+function(_, m)
   local D;
   D := MakeImmutable(BookGraph(IsMutableDigraph, m));
   SetIsMultiDigraph(D, false);
@@ -935,7 +935,7 @@ end);
 InstallMethod(StackedBookGraphCons,
 "for IsMutableDigraph and two positive integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local book;
   book := DigraphSymmetricClosure(ChainDigraph(IsMutable, n));
   return DigraphCartesianProduct(book, StarGraph(IsMutable, m + 1));
@@ -952,7 +952,7 @@ InstallMethod(StackedBookGraph, "for two positive integers",
 InstallMethod(StackedBookGraphCons,
 "for IsImmutableDigraph and two positive integers",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, m, n)
+function(_, m, n)
   local D;
   D := MakeImmutable(StackedBookGraph(IsMutableDigraph, m, n));
   SetIsMultiDigraph(D, false);
@@ -964,7 +964,7 @@ end);
 InstallMethod(BinaryTreeCons,
 "for IsMutableDigraph and positive integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, depth)
+function(_, depth)
   local D, x, i, j;
   D := [[]];
   for i in [1 .. depth - 1] do
@@ -979,7 +979,7 @@ end);
 InstallMethod(BinaryTreeCons,
 "for IsImmutableDigraph and positive integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, depth)
+function(_, depth)
   local D;
   D := BinaryTreeCons(IsMutableDigraph, depth);
   MakeImmutable(D);
@@ -994,7 +994,7 @@ InstallMethod(BinaryTree, "for a function and a positive integer",
 
 InstallMethod(AndrasfaiGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local js;
   js := List([0 .. (n - 1)], x -> (3 * x) + 1);
   return CirculantGraph(IsMutableDigraph, (3 * n) - 1, js);
@@ -1003,7 +1003,7 @@ end);
 InstallMethod(AndrasfaiGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(AndrasfaiGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1024,7 +1024,7 @@ InstallMethod(AndrasfaiGraph, "for a function and an integer",
 
 InstallMethod(BinomialTreeGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local bits, is2n, verts, D, rep, pos, parent, parVert, i;
   bits := Log(n, 2);
   is2n := IsEvenInt(n) and IsPrimePowerInt(n);
@@ -1050,7 +1050,7 @@ end);
 InstallMethod(BinomialTreeGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(BinomialTreeGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1068,7 +1068,7 @@ InstallMethod(BinomialTreeGraph, "for a function and an integer",
 
 InstallMethod(BondyGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsInt],
-function(filt, n)
+function(_, n)
   if n < 0 then
     ErrorNoReturn("the argument <n> must be a non-negative integer,");
   fi;
@@ -1078,7 +1078,7 @@ end);
 InstallMethod(BondyGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(BondyGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1095,7 +1095,7 @@ InstallMethod(BondyGraph, "for a function and an integer",
 
 InstallMethod(CirculantGraphCons, "for IsMutableDigraph, an integer and a list",
 [IsMutableDigraph, IsPosInt, IsList],
-function(filt, n, par)
+function(_, n, par)
   local D, i, j;
   if (n < 2) or (not ForAll(par, x -> IsInt(x) and x in [1 .. n])) then
     ErrorNoReturn("arguments must be an integer <n> greater ",
@@ -1123,7 +1123,7 @@ end);
 InstallMethod(CirculantGraphCons,
 "for IsImmutableDigraph, integer, list of integers",
 [IsImmutableDigraph, IsPosInt, IsList],
-function(filt, n, par)
+function(_, n, par)
   local D;
   D := MakeImmutable(CirculantGraphCons(IsMutableDigraph, n, par));
   SetIsMultiDigraph(D, false);
@@ -1154,7 +1154,7 @@ end);
 InstallMethod(CycleGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(CycleGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1170,7 +1170,7 @@ InstallMethod(CycleGraph, "for a function and an integer",
 
 InstallMethod(GearGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D, i, central;
   if n < 3 then
     ErrorNoReturn("the argument <n> must be an integer greater than 2,");
@@ -1188,7 +1188,7 @@ end);
 InstallMethod(GearGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(GearGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1204,7 +1204,7 @@ InstallMethod(GearGraph, "for a function and an integer",
 
 InstallMethod(HalvedCubeGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D, tuples, vertices, i, j;
   tuples := Tuples([0, 1], n);
   vertices := List([1 .. (2 ^ (n - 1))], x -> []);
@@ -1231,7 +1231,7 @@ end);
 InstallMethod(HalvedCubeGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(HalvedCubeGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1250,7 +1250,7 @@ InstallMethod(HalvedCubeGraph, "for a function and an integer",
 
 InstallMethod(HanoiGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D, nrVert, prevNrVert, exp, i;
   D := Digraph(IsMutableDigraph, []);
   nrVert := 3 ^ n;
@@ -1274,7 +1274,7 @@ end);
 InstallMethod(HanoiGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(HanoiGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1292,7 +1292,7 @@ InstallMethod(HanoiGraph, "for a function and an integer",
 
 InstallMethod(HelmGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   if n < 3 then
     ErrorNoReturn("the argument <n> must be an integer greater than 2,");
@@ -1307,7 +1307,7 @@ end);
 InstallMethod(HelmGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(HelmGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1324,7 +1324,7 @@ InstallMethod(HelmGraph, "for a function and an integer",
 InstallMethod(HypercubeGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(HypercubeGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1338,7 +1338,7 @@ end);
 
 InstallMethod(HypercubeGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsInt],
-function(filt, n)
+function(_, n)
   local D, vertices, i, j;
   if n < 0 then
     ErrorNoReturn("the argument <n> must be a non-negative integer,");
@@ -1365,7 +1365,7 @@ InstallMethod(HypercubeGraph, "for a function and an integer",
 
 InstallMethod(KellerGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsInt],
-function(filt, n)
+function(_, n)
   local D, vertices, i, j;
   if n < 0 then
     ErrorNoReturn("the argument <n> must be a non-negative integer,");
@@ -1390,7 +1390,7 @@ end);
 InstallMethod(KellerGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(KellerGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1412,7 +1412,7 @@ InstallMethod(KellerGraph, "for a function and an integer",
 
 InstallMethod(KneserGraphCons, "for IsMutableDigraph and two integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-function(filt, n, k)
+function(_, n, k)
   local D, vertices, i, j;
   if n < k then
     ErrorNoReturn("argument <n> must be greater than or equal to argument <k>,");
@@ -1433,7 +1433,7 @@ end);
 InstallMethod(KneserGraphCons,
 "for IsImmutableDigraph, integer, integer",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, n, k)
+function(_, n, k)
   local D;
   D := MakeImmutable(KneserGraphCons(IsMutableDigraph, n, k));
   SetIsMultiDigraph(D, false);
@@ -1462,7 +1462,7 @@ InstallMethod(KneserGraph, "for a function and two integers",
 
 InstallMethod(LindgrenSousselierGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D, central, i, threei;
   central := 6 * n + 4;
   D := CycleGraph(IsMutableDigraph, central - 1);
@@ -1484,7 +1484,7 @@ end);
 InstallMethod(LindgrenSousselierGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(LindgrenSousselierGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1501,7 +1501,7 @@ InstallMethod(LindgrenSousselierGraph, "for a function and an integer",
 
 InstallMethod(MobiusLadderGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D, i;
   if n < 4 then
     ErrorNoReturn("the argument <n> must be an integer equal to 4 or more,");
@@ -1517,7 +1517,7 @@ end);
 InstallMethod(MobiusLadderGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(MobiusLadderGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1533,7 +1533,7 @@ InstallMethod(MobiusLadderGraph, "for a function and an integer",
 
 InstallMethod(MycielskiGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D, i;
   if n < 2 then
     ErrorNoReturn("the argument <n> must be an integer greater than 1,");
@@ -1550,7 +1550,7 @@ end);
 InstallMethod(MycielskiGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(MycielskiGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1569,7 +1569,7 @@ InstallMethod(MycielskiGraph, "for a function and an integer",
 
 InstallMethod(OddGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsInt],
-function(filt, n)
+function(_, n)
   if n < 1 then
     ErrorNoReturn("the argument <n> must be an integer greater than 0,");
   fi;
@@ -1579,7 +1579,7 @@ end);
 InstallMethod(OddGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(OddGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1600,14 +1600,12 @@ InstallMethod(OddGraph, "for a function and an integer",
 
 InstallMethod(PathGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
-  return DigraphSymmetricClosure(ChainDigraph(IsMutableDigraph, n));
-end);
+{_, n} -> DigraphSymmetricClosure(ChainDigraph(IsMutableDigraph, n)));
 
 InstallMethod(PathGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(PathGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1625,7 +1623,7 @@ InstallMethod(PathGraph, "for a function and an integer",
 
 InstallMethod(PermutationStarGraphCons, "for IsMutableDigraph and two integers",
 [IsMutableDigraph, IsPosInt, IsInt],
-function(filt, n, k)
+function(_, n, k)
   local D, permList, vertices, bList, pos, i, j;
   if k < 0 then
     ErrorNoReturn("the arguments <n> and <k> must be integers, ",
@@ -1660,7 +1658,7 @@ end);
 InstallMethod(PermutationStarGraphCons,
 "for IsImmutableDigraph, integer, integer",
 [IsImmutableDigraph, IsPosInt, IsInt],
-function(filt, n, k)
+function(_, n, k)
   local D;
   D := MakeImmutable(PermutationStarGraphCons(IsMutableDigraph, n, k));
   SetIsMultiDigraph(D, false);
@@ -1683,7 +1681,7 @@ InstallMethod(PermutationStarGraph, "for a function and two integers",
 
 InstallMethod(PrismGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   if n < 3 then
     ErrorNoReturn("the argument <n> must be an integer equal to 3 or more,");
   else
@@ -1694,7 +1692,7 @@ end);
 InstallMethod(PrismGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(PrismGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1710,7 +1708,7 @@ InstallMethod(PrismGraph, "for a function and an integer",
 
 InstallMethod(StackedPrismGraphCons, "for IsMutableDigraph and two integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-function(filt, n, k)
+function(_, n, k)
   if n < 3 then
     ErrorNoReturn("the arguments <n> and <k> must be integers, ",
                   "with <n> greater than 2 and <k> greater than 0,");
@@ -1722,7 +1720,7 @@ end);
 InstallMethod(StackedPrismGraphCons,
 "for IsImmutableDigraph, integer, integer",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, n, k)
+function(_, n, k)
   local D;
   D := MakeImmutable(StackedPrismGraphCons(IsMutableDigraph, n, k));
   SetIsMultiDigraph(D, false);
@@ -1738,7 +1736,7 @@ InstallMethod(StackedPrismGraph, "for a function and two integers",
 
 InstallMethod(WalshHadamardGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local H_2, H_n, i, D, j, sideHn;
   H_2 := [[1, 1],
           [1, -1]];
@@ -1767,7 +1765,7 @@ end);
 InstallMethod(WalshHadamardGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(WalshHadamardGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1784,7 +1782,7 @@ InstallMethod(WalshHadamardGraph, "for a function and an integer",
 
 InstallMethod(WebGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D, i;
   if n < 3 then
     ErrorNoReturn("the argument <n> must be an integer greater than 2,");
@@ -1801,7 +1799,7 @@ end);
 InstallMethod(WebGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(WebGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1817,7 +1815,7 @@ InstallMethod(WebGraph, "for a function and an integer",
 
 InstallMethod(WheelGraphCons, "for IsMutableDigraph and an integer",
 [IsMutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   if n < 4 then
     ErrorNoReturn("the argument <n> must be an integer greater than 3,");
@@ -1832,7 +1830,7 @@ end);
 InstallMethod(WheelGraphCons,
 "for IsImmutableDigraph, integer",
 [IsImmutableDigraph, IsPosInt],
-function(filt, n)
+function(_, n)
   local D;
   D := MakeImmutable(WheelGraphCons(IsMutableDigraph, n));
   SetIsMultiDigraph(D, false);
@@ -1855,7 +1853,7 @@ InstallMethod(WheelGraph, "for a function and an integer",
 
 InstallMethod(WindmillGraphCons, "for IsMutableDigraph and two integers",
 [IsMutableDigraph, IsPosInt, IsPosInt],
-function(filt, n, m)
+function(_, n, m)
   local D, i, K, nrVert;
   if m < 2 or n < 2 then
     ErrorNoReturn("the arguments <n> and <m> must be integers greater than 1,");
@@ -1877,7 +1875,7 @@ end);
 InstallMethod(WindmillGraphCons,
 "for IsImmutableDigraph, integer, integer",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(filt, n, m)
+function(_, n, m)
   local D;
   D := MakeImmutable(WindmillGraphCons(IsMutableDigraph, n, m));
   SetIsMultiDigraph(D, false);
diff --git a/gap/grahom.gi b/gap/grahom.gi
index 806c802d4..1b7d854b6 100644
--- a/gap/grahom.gi
+++ b/gap/grahom.gi
@@ -475,9 +475,8 @@ end);
 
 InstallMethod(DigraphsRespectsColouring,
 [IsDigraph, IsDigraph, IsPerm, IsList, IsList],
-function(src, ran, x, cols1, cols2)
-  return DigraphsRespectsColouring(src, ran, AsTransformation(x), cols1, cols2);
-end);
+{src, ran, x, cols1, cols2}
+-> DigraphsRespectsColouring(src, ran, AsTransformation(x), cols1, cols2));
 
 InstallMethod(IsDigraphHomomorphism,
 "for a digraph by out-neighbours, a digraph, and a perm",
@@ -728,7 +727,7 @@ function(D1, D2)
   L := MaximalCommonSubdigraph(D1, D2);
   L[2] := List([1 .. DigraphNrVertices(L[1])], x -> x ^ L[2]);
   L[3] := List([1 .. DigraphNrVertices(L[1])], x -> x ^ L[3]);
-  out := List(OutNeighbours(D1), x -> ShallowCopy(x));
+  out := List(OutNeighbours(D1), ShallowCopy);
   newvertices := Filtered(DigraphVertices(D2), x -> not x in L[3]);
   embedding1 := [1 .. DigraphNrVertices(D1)];
 
@@ -822,7 +821,7 @@ function(L1, L2)
     return next;
   end;
 
-  Recurse := function(last_defined, depth, print)
+  Recurse := function(depth, print)
     local next, value, try_next_value, prev, x;
 
     if depth = N1 + 1 then  # When depth = N1 + 1, we have defined all images
@@ -879,7 +878,7 @@ function(L1, L2)
             FlipBlist(in2[value]);
           fi;
         od;
-        if Recurse(next, depth + 1, print) then
+        if Recurse(depth + 1, print) then
           return true;
         fi;
       fi;
@@ -892,7 +891,7 @@ function(L1, L2)
     return false;
   end;
 
-  if Recurse(1, 1, false) then
+  if Recurse(1, false) then
     Append(map, [N1 + 1 .. N2]);
     return p ^ -1 * Transformation(map);
   fi;
@@ -926,9 +925,7 @@ function(L1, L2, map)
 
   if join2 = fail or meet2 = fail then
     ErrorNoReturn("the 2nd argument (a digraph) must be a lattice digraph");
-  fi;
-
-  if Maximum(ImageSetOfTransformation(map, N1)) > N2 then
+  elif Maximum(ImageSetOfTransformation(map, N1)) > N2 then
     return false;
   fi;
   # The above checks if the <x ^ map> and <y ^ map> entries of
diff --git a/gap/grape.gi b/gap/grape.gi
index e629e0e29..6b1f158fc 100644
--- a/gap/grape.gi
+++ b/gap/grape.gi
@@ -77,9 +77,7 @@ function(imm, G, obj, act, adj)
   D := DigraphNC(imm, out);
 
   if IsImmutableDigraph(D) then
-    adj_func := function(u, v)
-      return adj(obj[u], obj[v]);
-    end;
+    adj_func := {u, v} -> adj(obj[u], obj[v]);
     SetFilterObj(D, IsDigraphWithAdjacencyFunction);
     SetDigraphAdjacencyFunction(D, adj_func);
     SetDigraphGroup(D, Range(hom));
diff --git a/gap/io.gi b/gap/io.gi
index 59df19285..ebf3b0310 100644
--- a/gap/io.gi
+++ b/gap/io.gi
@@ -209,7 +209,8 @@ function(arg)
     fi;
   end;
 
-  record.ShallowCopy := function(iter)
+  # TODO store filename, decoder in iter?
+  record.ShallowCopy := function(_)
     local file;
     file := DigraphFile(UserHomeExpand(filename), decoder, "r");
     return rec(file := file, current := file!.coder(file));
@@ -595,7 +596,7 @@ end);
 
 InstallMethod(DigraphFromGraph6StringCons, "for IsMutableDigraph and a string",
 [IsMutableDigraph, IsString],
-function(func, s)
+function(filt, s)
   local FindCoord, list, n, start, maxedges, out, pos, nredges, i, bpos, edge,
   j;
 
@@ -672,13 +673,13 @@ function(func, s)
     od;
     pos := pos + 6;
   od;
-  return DigraphNC(IsMutableDigraph, out);
+  return DigraphNC(filt, out);
 end);
 
 InstallMethod(DigraphFromGraph6StringCons,
 "for IsImmutableDigraph and a string",
 [IsImmutableDigraph, IsString],
-function(filt, s)
+function(_, s)
   local D;
   D := MakeImmutable(DigraphFromGraph6StringCons(IsMutableDigraph, s));
   SetIsSymmetricDigraph(D, true);
@@ -696,7 +697,7 @@ s -> DigraphFromGraph6String(IsImmutableDigraph, s));
 
 InstallMethod(DigraphFromDigraph6StringCons, "for IsMutableDigraph and a string",
 [IsMutableDigraph, IsString],
-function(func, s)
+function(filt, s)
   local legacy, list, n, start, i, range, source, pos, len, j, bpos, tabpos;
   # NOTE: this package originally used a version of digraph6 that reads down
   # the columns of an adjacency matrix, and appends a '+' to the start.  This
@@ -775,12 +776,12 @@ function(func, s)
   od;
 
   if legacy then  # source and range are reversed
-    return DigraphNC(IsMutableDigraph,
+    return DigraphNC(filt,
                  rec(DigraphNrVertices := n,
                      DigraphSource     := range,
                      DigraphRange      := source));
   fi;
-  return DigraphNC(IsMutableDigraph,
+  return DigraphNC(filt,
                rec(DigraphNrVertices := n,
                    DigraphRange      := range,
                    DigraphSource     := source));
@@ -800,7 +801,7 @@ InstallMethod(DigraphFromDigraph6String, "for a string",
 
 InstallMethod(DigraphFromSparse6StringCons, "for IsMutableDigraph and a string",
 [IsMutableDigraph, IsString],
-function(func, s)
+function(filt, s)
   local list, n, start, blist, pos, num, bpos, k, range, source, len, v, i,
   finish, x, j;
 
@@ -908,7 +909,7 @@ function(func, s)
 
   range := range + 1;
   source := source + 1;
-  return DigraphNC(IsMutableDigraph, (rec(DigraphNrVertices := n,
+  return DigraphNC(filt, (rec(DigraphNrVertices := n,
                                       DigraphRange := range,
                                       DigraphSource := source)));
 end);
@@ -916,7 +917,7 @@ end);
 InstallMethod(DigraphFromSparse6StringCons,
 "for IsImmutableDigraph and a string",
 [IsImmutableDigraph, IsString],
-function(filt, s)
+function(_, s)
   local D;
   D := MakeImmutable(DigraphFromSparse6String(IsMutableDigraph, s));
   SetIsSymmetricDigraph(D, true);
@@ -924,8 +925,7 @@ function(filt, s)
 end);
 
 InstallMethod(DigraphFromSparse6String, "for a function and a string",
-[IsFunction, IsString],
-DigraphFromSparse6StringCons);
+[IsFunction, IsString], DigraphFromSparse6StringCons);
 
 InstallMethod(DigraphFromSparse6String, "for a string",
 [IsString],
@@ -1059,9 +1059,9 @@ function(func, s)
   od;
   range := range + 1;
   source := source + 1;
-  return DigraphNC(IsMutableDigraph, (rec(DigraphNrVertices := n,
-                                      DigraphRange      := range,
-                                      DigraphSource     := source)));
+  return DigraphNC(func, (rec(DigraphNrVertices := n,
+                              DigraphRange      := range,
+                              DigraphSource     := source)));
 end);
 
 InstallMethod(DigraphFromDiSparse6StringCons,
@@ -1102,21 +1102,19 @@ InstallMethod(DigraphFromPlainTextStringCons,
 "for IsMutableDigraph and a string", [IsMutableDigraph, IsString],
 function(filt, s)
   local f;
-  f := x -> DigraphByEdges(IsMutableDigraph, x);
+  f := x -> DigraphByEdges(filt, x);
   return DIGRAPHS_PlainTextLineDecoder(f, "  ", " ", 1)(Chomp(s));
 end);
 
 InstallMethod(DigraphFromPlainTextStringCons,
 "for IsImmutableDigraph and a string", [IsImmutableDigraph, IsString],
-{filt, s} -> MakeImmutable(DigraphFromPlainTextStringCons(IsMutableDigraph, s)));
+{_, s} -> MakeImmutable(DigraphFromPlainTextStringCons(IsMutableDigraph, s)));
 
 InstallMethod(DigraphFromPlainTextString, "for a function and a string",
-[IsFunction, IsString],
-DigraphFromPlainTextStringCons);
+[IsFunction, IsString], DigraphFromPlainTextStringCons);
 
 InstallMethod(DigraphFromPlainTextString, "for a string",
-[IsString],
-s -> DigraphFromPlainTextString(IsImmutableDigraph, s));
+[IsString], s -> DigraphFromPlainTextString(IsImmutableDigraph, s));
 
 # DIMACS format: for symmetric digraphs, one per file, can have loops and
 # multiple edges.
@@ -1610,10 +1608,20 @@ function(D)
   return List(list, i -> CharInt(i + 63));
 end);
 
+BindGlobal("DIGRAPHS_AddBinary",
+function(blist, k, nextbit, i)
+  local b;
+  for b in [1 .. k] do
+    blist[nextbit] := Int((i mod (2 ^ (k - b + 1))) / (2 ^ (k - b))) = 1;
+    nextbit := nextbit + 1;
+  od;
+  return nextbit;
+end);
+
 InstallMethod(Sparse6String, "for a digraph by out-neighbours",
 [IsDigraphByOutNeighboursRep],
 function(D)
-  local list, n, lenlist, adj, nredges, k, blist, v, nextbit, AddBinary, i, j,
+  local list, n, lenlist, adj, nredges, k, blist, v, nextbit, i, j,
         bitstopad, pos, block;
   if not IsSymmetricDigraph(D) then
     ErrorNoReturn("the argument <D> must be a symmetric digraph,");
@@ -1648,13 +1656,6 @@ function(D)
   blist := BlistList([1 .. nredges * (k + 1) / 2], []);
   v := 0;
   nextbit := 1;
-  AddBinary := function(blist, i)
-    local b;
-    for b in [1 .. k] do
-      blist[nextbit] := Int((i mod (2 ^ (k - b + 1))) / (2 ^ (k - b))) = 1;
-      nextbit := nextbit + 1;
-    od;
-  end;
   for i in [1 .. Length(adj)] do
     for j in adj[i] do
       if i < j then
@@ -1668,13 +1669,12 @@ function(D)
         v := v + 1;
       elif i > v + 2 then
         blist[nextbit] := true;
-        nextbit := nextbit + 1;
-        AddBinary(blist, i - 1);
+        nextbit := DIGRAPHS_AddBinary(blist, k, nextbit + 1, i - 1);
         v := i - 1;
         blist[nextbit] := false;
         nextbit := nextbit + 1;
       fi;
-      AddBinary(blist, j - 1);
+      nextbit := DIGRAPHS_AddBinary(blist, k, nextbit, j - 1);
     od;
   od;
 
@@ -1721,7 +1721,7 @@ InstallMethod(DiSparse6String, "for a digraph by out-neighbours",
 [IsDigraphByOutNeighboursRep],
 function(D)
   local list, n, lenlist, adj, source_i, range_i, source_d, range_d, len1,
-  len2, sort_d, perm, sort_i, k, blist, v, nextbit, AddBinary, bitstopad,
+  len2, sort_d, perm, sort_i, k, blist, v, nextbit, bitstopad,
   pos, block, i, j;
 
   list := [];
@@ -1800,13 +1800,6 @@ function(D)
   blist := [];
   v := 0;
   nextbit := 1;
-  AddBinary := function(blist, i)
-    local b;
-    for b in [1 .. k] do
-      blist[nextbit] := Int((i mod (2 ^ (k - b + 1))) / (2 ^ (k - b))) = 1;
-      nextbit := nextbit + 1;
-    od;
-  end;
   for i in [1 .. Length(source_d)] do
     if source_d[i] = v then
       blist[nextbit] := false;
@@ -1817,19 +1810,17 @@ function(D)
       v := v + 1;
     elif source_d[i] > v + 1 then  # is this check necessary
       blist[nextbit] := true;
-      nextbit := nextbit + 1;
-      AddBinary(blist, source_d[i]);
+      nextbit := DIGRAPHS_AddBinary(blist, k, nextbit + 1, source_d[i]);
       v := source_d[i];
       blist[nextbit] := false;
       nextbit := nextbit + 1;
     fi;
-    AddBinary(blist, range_d[i]);
+    nextbit := DIGRAPHS_AddBinary(blist, k, nextbit, range_d[i]);
   od;
 
   # Add a separation symbol (1 n).
   blist[nextbit] := true;
-  nextbit := nextbit + 1;
-  AddBinary(blist, n);
+  nextbit := DIGRAPHS_AddBinary(blist, k, nextbit + 1, n);
 
   # Repeat everything for increasing edges
   v := 0;
@@ -1843,13 +1834,12 @@ function(D)
       v := v + 1;
     elif range_i[i] > v + 1 then  # is this check necessary
       blist[nextbit] := true;
-      nextbit := nextbit + 1;
-      AddBinary(blist, range_i[i]);
+      nextbit := DIGRAPHS_AddBinary(blist, k, nextbit + 1, range_i[i]);
       v := range_i[i];
       blist[nextbit] := false;
       nextbit := nextbit + 1;
     fi;
-    AddBinary(blist, source_i[i]);
+    nextbit := DIGRAPHS_AddBinary(blist, k, nextbit, source_i[i]);
   od;
 
   # Add padding bits:
diff --git a/gap/isomorph.gi b/gap/isomorph.gi
index 119dec136..d00bef066 100644
--- a/gap/isomorph.gi
+++ b/gap/isomorph.gi
@@ -117,7 +117,7 @@ end);
 ## Returns a list where the first position is the automorphism group, and the
 ## second is the canonical labelling.
 BindGlobal("BLISS_DATA",
-function(D, vert_colours, edge_colours, calling_function_name)
+function(D, vert_colours, edge_colours)
   if vert_colours <> fail then
     vert_colours := DIGRAPHS_ValidateVertexColouring(DigraphNrVertices(D),
                                                      vert_colours);
@@ -128,10 +128,7 @@ function(D, vert_colours, edge_colours, calling_function_name)
   return BLISS_DATA_NC(D, vert_colours, edge_colours);
 end);
 
-BindGlobal("BLISS_DATA_NO_COLORS",
-function(D)
-  return BLISS_DATA(D, fail, fail, "");
-end);
+BindGlobal("BLISS_DATA_NO_COLORS", D -> BLISS_DATA(D, fail, fail));
 
 if DIGRAPHS_NautyAvailable then
   BindGlobal("NAUTY_DATA",
@@ -181,12 +178,7 @@ end);
 
 InstallMethod(BlissCanonicalLabelling, "for a digraph and vertex coloring",
 [IsDigraph, IsHomogeneousList],
-function(D, colors)
-  return BLISS_DATA(D,
-                    colors,
-                    fail,
-                    "BlissCanonicalLabelling")[2];
-end);
+{D, colors} -> BLISS_DATA(D, colors, fail)[2]);
 
 InstallMethod(NautyCanonicalLabelling, "for a digraph",
 [IsDigraph],
@@ -292,23 +284,13 @@ function(D)
 end);
 
 InstallMethod(BlissAutomorphismGroup, "for a digraph and vertex coloring",
-[IsDigraph, IsHomogeneousList],
-function(D, colors)
-  return BLISS_DATA(D,
-                    colors,
-                    fail,
-                    "AutomorphismGroup")[1];
-end);
+[IsDigraph, IsHomogeneousList], {D, colors} -> BLISS_DATA(D, colors, fail)[1]);
 
 InstallMethod(BlissAutomorphismGroup,
 "for a digraph, vertex colouring, and edge colouring",
 [IsDigraph, IsHomogeneousList, IsList],
-function(digraph, vert_colours, edge_colours)
-  return BLISS_DATA(digraph,
-                    vert_colours,
-                    edge_colours,
-                    "AutomorphismGroup")[1];
-end);
+{digraph, vert_colours, edge_colours}
+-> BLISS_DATA(digraph, vert_colours, edge_colours)[1]);
 
 InstallMethod(BlissAutomorphismGroup,
 "for a digraph, fail, and edge colouring",
@@ -317,10 +299,7 @@ function(digraph, vert_colours, edge_colours)
   if not vert_colours = fail then
     TryNextMethod();
   fi;
-  return BLISS_DATA(digraph,
-                    vert_colours,
-                    edge_colours,
-                    "AutomorphismGroup")[1];
+  return BLISS_DATA(digraph, vert_colours, edge_colours)[1];
 end);
 
 InstallMethod(NautyAutomorphismGroup, "for a digraph and vertex coloring",
diff --git a/gap/labels.gi b/gap/labels.gi
index 17965083a..0018963ef 100644
--- a/gap/labels.gi
+++ b/gap/labels.gi
@@ -79,9 +79,7 @@ function(D)
 end);
 
 InstallMethod(HaveEdgeLabelsBeenAssigned, "for a digraph", [IsDigraph],
-function(D)
-  return IsBound(D!.edgelabels);
-end);
+D -> IsBound(D!.edgelabels));
 
 InstallMethod(SetDigraphEdgeLabel,
 "for a digraph, a pos int, a pos int, and an object",
diff --git a/gap/oper.gi b/gap/oper.gi
index 5273dcd0b..5186a7d3f 100644
--- a/gap/oper.gi
+++ b/gap/oper.gi
@@ -193,9 +193,8 @@ end);
 InstallMethod(DigraphAddEdge,
 "for an immutable digraph and two positive integers",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(D, src, ran)
-  return MakeImmutable(DigraphAddEdge(DigraphMutableCopy(D), src, ran));
-end);
+{D, src, ran}
+-> MakeImmutable(DigraphAddEdge(DigraphMutableCopy(D), src, ran)));
 
 InstallMethod(DigraphAddEdge, "for a mutable digraph and a list",
 [IsMutableDigraph, IsList],
@@ -250,9 +249,8 @@ end);
 InstallMethod(DigraphRemoveEdge,
 "for a immutable digraph and two positive integers",
 [IsImmutableDigraph, IsPosInt, IsPosInt],
-function(D, src, ran)
-  return MakeImmutable(DigraphRemoveEdge(DigraphMutableCopy(D), src, ran));
-end);
+{D, src, ran}
+-> MakeImmutable(DigraphRemoveEdge(DigraphMutableCopy(D), src, ran)));
 
 InstallMethod(DigraphRemoveEdge, "for a mutable digraph and a list",
 [IsMutableDigraph, IsList],
@@ -619,7 +617,8 @@ InstallMethod(ModularProduct, "for a digraph and digraph",
 function(D1, D2)
   local edge_function;
 
-  edge_function := function(u, v, m, n, map)
+  edge_function := function(u, v, m, n, map)  # gaplint: disable=W000
+    # neither m nor n is used, but can't replace them both with _
     local w, x, connections;
     connections := [];
     for w in OutNeighbours(D1)[u] do
@@ -647,7 +646,8 @@ InstallMethod(StrongProduct, "for a digraph and digraph",
 function(D1, D2)
   local edge_function;
 
-  edge_function := function(u, v, m, n, map)
+  edge_function := function(u, v, m, n, map)  # gaplint: disable=W000
+    # neither m nor n is used, but can't replace them both with _
     local w, x, connections;
       connections := [];
       for x in OutNeighbours(D2)[v] do
@@ -694,7 +694,7 @@ InstallMethod(HomomorphicProduct, "for a digraph and digraph",
 function(D1, D2)
   local edge_function;
 
-  edge_function := function(u, v, m, n, map)
+  edge_function := function(u, v, _, n, map)
     local w, x, connections;
       connections := [];
       for x in [1 .. n] do
@@ -716,7 +716,7 @@ InstallMethod(LexicographicProduct, "for a digraph and digraph",
 function(D1, D2)
   local edge_function;
 
-  edge_function := function(u, v, m, n, map)
+  edge_function := function(u, v, _, n, map)
     local w, x, connections;
       connections := [];
       for w in OutNeighbours(D1)[u] do
@@ -752,9 +752,7 @@ function(D1, D2, edge_function)
 
   edges := EmptyPlist(m * n);
 
-  map := function(a, b)
-    return (a - 1) * n + b;
-  end;
+  map := {a, b} -> (a - 1) * n + b;
 
   for u in [1 .. m] do
     for v in [1 .. n] do
@@ -984,9 +982,8 @@ end);
 InstallMethod(QuotientDigraph,
 "for an immutable digraph and a homogeneous list",
 [IsImmutableDigraph, IsHomogeneousList],
-function(D, partition)
-  return MakeImmutable(QuotientDigraph(DigraphMutableCopy(D), partition));
-end);
+{D, partition} ->
+MakeImmutable(QuotientDigraph(DigraphMutableCopy(D), partition)));
 
 #############################################################################
 # 6. In and out degrees, neighbours, and edges of vertices
@@ -2198,9 +2195,7 @@ function(D, i, j)
 
   if HasDigraphJoinTable(D) then
     return DigraphJoinTable(D)[i, j];
-  fi;
-
-  if not IsPartialOrderDigraph(D) then
+  elif not IsPartialOrderDigraph(D) then
     ErrorNoReturn("the 1st argument <D> must satisfy ",
                   "IsPartialOrderDigraph,");
   elif not i in DigraphVertices(D) then
@@ -2230,9 +2225,7 @@ function(D, i, j)
 
   if HasDigraphMeetTable(D) then
     return DigraphMeetTable(D)[i, j];
-  fi;
-
-  if not IsPartialOrderDigraph(D) then
+  elif not IsPartialOrderDigraph(D) then
     ErrorNoReturn("the 1st argument <D> must satisfy ",
                   "IsPartialOrderDigraph,");
   elif not i in DigraphVertices(D) then
diff --git a/gap/orbits.gi b/gap/orbits.gi
index c3bfe4867..eefc39e5c 100644
--- a/gap/orbits.gi
+++ b/gap/orbits.gi
@@ -87,7 +87,7 @@ function(D)
   return out;
 end);
 
-InstallImmediateMethod(DigraphGroup, IsDigraph and HasAutomorphismGroup, 0,
+BindGlobal("DIGRAPHS_DigraphGroup",
 function(D)
   if IsMultiDigraph(D) then
     return Range(Projection(AutomorphismGroup(D), 1));
@@ -95,14 +95,10 @@ function(D)
   return AutomorphismGroup(D);
 end);
 
-InstallMethod(DigraphGroup, "for a digraph",
-[IsDigraph],
-function(D)
-  if IsMultiDigraph(D) then
-    return Range(Projection(AutomorphismGroup(D), 1));
-  fi;
-  return AutomorphismGroup(D);
-end);
+InstallImmediateMethod(DigraphGroup, IsDigraph and HasAutomorphismGroup, 0,
+DIGRAPHS_DigraphGroup);
+
+InstallMethod(DigraphGroup, "for a digraph", [IsDigraph], DIGRAPHS_DigraphGroup);
 
 InstallMethod(DigraphOrbits, "for a digraph",
 [IsDigraph],
diff --git a/gap/prop.gi b/gap/prop.gi
index 6f29c6fe1..0f4fd0d18 100644
--- a/gap/prop.gi
+++ b/gap/prop.gi
@@ -623,7 +623,7 @@ function(D)
   # complete digraph on 2 vertices.
 
   proper_endo_found := false;
-  hook := function(unneded_argument, T)
+  hook := function(_, T)
     # the hook is required by HomomorphismDigraphsFinder to have two arguments,
     # the 1st of which is user_param, which this method doesn't need.
     if RankOfTransformation(T, [1 .. N]) < N then
diff --git a/gap/utils.gi b/gap/utils.gi
index 1b3ded314..841c8073e 100644
--- a/gap/utils.gi
+++ b/gap/utils.gi
@@ -34,11 +34,7 @@ function()
 end);
 
 InstallGlobalFunction(DIGRAPHS_Test,
-function(filename)
-  return DIGRAPHS_RunTest(function()
-                            return Test(filename, rec(showProgress := false));
-                          end);
-end);
+fname -> DIGRAPHS_RunTest({} -> Test(fname, rec(showProgress := false))));
 
 # The parameter <func> should be a 0-argument function which returns true or
 # false.
@@ -106,10 +102,7 @@ function()
                          "main.xml", DIGRAPHS_DocXMLFiles, "Single");
 end);
 
-InstallGlobalFunction(DIGRAPHS_Dir,
-function()
-  return GAPInfo.PackagesLoaded.digraphs[1];
-end);
+InstallGlobalFunction(DIGRAPHS_Dir, {} -> GAPInfo.PackagesLoaded.digraphs[1]);
 
 #############################################################################
 # User facing stuff
@@ -163,9 +156,7 @@ function(arg)
   fi;
 
   dir := DirectoriesPackageLibrary("digraphs", "tst/standard/");
-  return DIGRAPHS_RunTest(function()
-                            return TestDirectory(dir, opts);
-                          end);
+  return DIGRAPHS_RunTest({} -> TestDirectory(dir, opts));
 end);
 
 InstallGlobalFunction(DigraphsTestExtreme,
@@ -207,9 +198,7 @@ function(arg)
   fi;
 
   dir := DirectoriesPackageLibrary("digraphs", "tst/extreme/");
-  return DIGRAPHS_RunTest(function()
-                            return TestDirectory(dir, opts);
-                          end);
+  return DIGRAPHS_RunTest({} -> TestDirectory(dir, opts));
 end);
 
 InstallGlobalFunction(DigraphsMakeDoc,
diff --git a/tst/extreme/oper.tst b/tst/extreme/oper.tst
index e388e1132..82b9aeb31 100644
--- a/tst/extreme/oper.tst
+++ b/tst/extreme/oper.tst
@@ -113,15 +113,15 @@ gap> list := ReadDigraphs(Concatenation(DIGRAPHS_Dir(),
 > "/digraphs-lib/fining.p.gz"));;
 gap> gr := list[4];;
 gap> gr2 := DigraphCopy(gr);;
-gap> layers1 := List(DigraphLayers(gr, 1), x -> Set(x));;
-gap> layers2 := List(DigraphLayers(gr2, 1), x -> Set(x));;
+gap> layers1 := List(DigraphLayers(gr, 1), Set);;
+gap> layers2 := List(DigraphLayers(gr2, 1), Set);;
 gap> layers1 = layers2;
 true
 gap> layers := [];;
 gap> for i in list do
 > Add(layers, DigraphLayers(i, 1));
 > od;
-gap> List(layers, x -> Size(x));
+gap> List(layers, Size);
 [ 3, 3, 5, 5, 7, 9 ]
 gap> gr := list[4];;
 gap> DigraphLayers(gr, 1);
diff --git a/tst/standard/digraph.tst b/tst/standard/digraph.tst
index 06a99877b..20933e2ca 100644
--- a/tst/standard/digraph.tst
+++ b/tst/standard/digraph.tst
@@ -684,8 +684,8 @@ gap> D := [
 > "&G~sC~EocF?oC", "&F~lQG{IB?_", "&G~s[~EocF?oC", "&G~tKpCO{D?oC",
 > "&F~jrGcMB?_", "&I~|SrNCKNoR?{@OB?C", "&F~lQG{IB?_", "&F~irgcIB?_",
 > "&F~kqG{IB?_"];;
-gap> D := List(D, x -> DigraphFromDigraph6String(x));;
-gap> iso := [];; 
+gap> D := List(D, DigraphFromDigraph6String);;
+gap> iso := [];;
 gap> iso_distr := [];;
 gap> eq := [];;
 gap> eq_distr := [];;
@@ -1523,7 +1523,7 @@ gap> gr;
 gap> Size(T);
 32
 gap> D := GreensDClasses(T);;
-gap> List(D, x -> Size(x));
+gap> List(D, Size);
 [ 6, 24, 2 ]
 gap> for i in [1 .. 3] do
 > for j in [1 .. 3] do
@@ -1550,7 +1550,7 @@ gap> T := AsSemigroup(IsPartialPermSemigroup, gr2, [G1, G2, G3, G4],
 > [[1, 3, hom13], [2, 3, hom23], [4, 1, hom41], [4, 2, hom42]]);;
 gap> Size(T);
 56
-gap> List(GreensDClasses(T), x -> Size(x));
+gap> List(GreensDClasses(T), Size);
 [ 6, 24, 2, 24 ]
 gap> List(GreensDClasses(T), x -> Size(x) = Size(GroupHClassOfGreensDClass(x)));
 [ true, true, true, true ]
@@ -1572,7 +1572,7 @@ gap> T := AsSemigroup(IsPartialPermSemigroup, gr4, [G1, G2, G3, G4, G5],
 > [[2, 1, hom21], [3, 1, hom31], [4, 1, hom41], [5, 2, hom52], [5, 3, hom53]]);;
 gap> Size(T);
 90
-gap> List(GreensDClasses(T), x -> Size(x));
+gap> List(GreensDClasses(T), Size);
 [ 24, 24, 6, 24, 12 ]
 gap> U := AsSemigroup(IsPartialPermSemigroup,
 > DigraphReverse(gr4),
diff --git a/tst/standard/io.tst b/tst/standard/io.tst
index 3439b0cdd..ad77eec19 100644
--- a/tst/standard/io.tst
+++ b/tst/standard/io.tst
@@ -33,7 +33,7 @@ gap> DigraphFromGraph6String(str);
 <immutable symmetric digraph with 5 vertices, 6 edges>
 gap>  l := ["BW", "C]", "DQw", "ECO_", "FCZUo", "GCZenS", "HCQTndn",
 > "H?qcyxf"];;
-gap> List(l, x -> DigraphFromGraph6String(x));
+gap> List(l, DigraphFromGraph6String);
 [ <immutable symmetric digraph with 3 vertices, 4 edges>, 
   <immutable symmetric digraph with 4 vertices, 8 edges>, 
   <immutable symmetric digraph with 5 vertices, 10 edges>, 
@@ -234,7 +234,7 @@ IO_OK
 
 # Note that some vertices in gr[2] are lost due to the file format not
 # supporting isolated vertices (i.e. vertices exist only because they are
-# involved in an edge). 
+# involved in an edge).
 gap> filename := Concatenation(DIGRAPHS_Dir(), "/tst/out/test.txt");;
 gap> ReadDigraphs(filename);
 [ <immutable digraph with 5 vertices, 7 edges>, 
@@ -471,7 +471,7 @@ Error, the 2nd argument <s> must be a non-empty string,
 gap> DigraphFromDiSparse6String("");
 Error, the 2nd argument <s> must be a non-empty string,
 
-#  DiSparse6 
+#  DiSparse6
 gap> DigraphFromDiSparse6String("I'm a string");
 Error, the 2nd argument <s> is not a valid disparse6 string,
 gap> DigraphFromDiSparse6String(".~~");
@@ -488,7 +488,7 @@ gap> gr := Digraph([[], [], [1, 2]]);;
 gap> DiSparse6String(gr);
 ".BoN"
 
-#  Plain text encoding  
+#  Plain text encoding
 gap> gr := CompleteDigraph(3);
 <immutable complete digraph with 3 vertices>
 gap> str := PlainTextString(gr);
diff --git a/tst/standard/oper.tst b/tst/standard/oper.tst
index beb378aaf..80086203b 100644
--- a/tst/standard/oper.tst
+++ b/tst/standard/oper.tst
@@ -980,7 +980,7 @@ gap> gr := DigraphAddEdges(gr, [[2, 3], [5, 6], [9, 10]]);
 gap> gr = ChainDigraph(14);
 true
 gap> n := 10;;
-gap> DigraphDisjointUnion(List([1 .. n], x -> EmptyDigraph(x))) =
+gap> DigraphDisjointUnion(List([1 .. n], EmptyDigraph)) =
 > EmptyDigraph(Int(n * (n + 1) / 2));
 true
 gap> D1 := CycleDigraph(3);; D2 := DigraphReverse(D1);;