diff --git a/gap/cliques.gi b/gap/cliques.gi
index fced5e253..56f58f3ca 100644
--- a/gap/cliques.gi
+++ b/gap/cliques.gi
@@ -126,7 +126,7 @@ end);
 ################################################################################
 
 InstallGlobalFunction(DigraphMaximalIndependentSet,
-function(arg)
+function(arg...)
   if IsEmpty(arg) then
     ErrorNoReturn("at least 1 argument is required,");
   elif not IsDigraph(arg[1]) then
@@ -141,7 +141,7 @@ function(arg)
 end);
 
 InstallGlobalFunction(DigraphIndependentSet,
-function(arg)
+function(arg...)
   if IsEmpty(arg) then
     ErrorNoReturn("at least 1 argument is required,");
   elif not IsDigraph(arg[1]) then
@@ -158,7 +158,7 @@ end);
 # Independent sets orbit representatives
 
 InstallGlobalFunction(DigraphIndependentSetsReps,
-function(arg)
+function(arg...)
   if IsEmpty(arg) then
     ErrorNoReturn("at least 1 argument is required,");
   elif not IsDigraph(arg[1]) then
@@ -175,7 +175,7 @@ InstallMethod(DigraphIndependentSetsAttr, "for a digraph", [IsDigraph],
 DigraphIndependentSets);
 
 InstallGlobalFunction(DigraphIndependentSets,
-function(arg)
+function(arg...)
   local D, out;
   if IsEmpty(arg) then
     ErrorNoReturn("at least 1 argument is required,");
@@ -202,7 +202,7 @@ InstallMethod(DigraphMaximalIndependentSetsRepsAttr, "for a digraph",
 [IsDigraph], DigraphMaximalIndependentSetsReps);
 
 InstallGlobalFunction(DigraphMaximalIndependentSetsReps,
-function(arg)
+function(arg...)
   local out, D;
   if IsEmpty(arg) then
     ErrorNoReturn("at least 1 argument is required,");
@@ -229,7 +229,7 @@ InstallMethod(DigraphMaximalIndependentSetsAttr, "for a digraph", [IsDigraph],
 DigraphMaximalIndependentSets);
 
 InstallGlobalFunction(DigraphMaximalIndependentSets,
-function(arg)
+function(arg...)
   local D, out;
   if IsEmpty(arg) then
     ErrorNoReturn("at least 1 argument is required,");
@@ -254,7 +254,7 @@ end);
 # Cliques
 
 InstallGlobalFunction(DigraphMaximalClique,
-function(arg)
+function(arg...)
   if IsEmpty(arg) then
     ErrorNoReturn("at least 1 argument is required,");
   fi;
@@ -263,7 +263,7 @@ function(arg)
 end);
 
 InstallGlobalFunction(DigraphClique,
-function(arg)
+function(arg...)
   if IsEmpty(arg) then
     ErrorNoReturn("at least 1 argument is required,");
   fi;
@@ -272,7 +272,7 @@ function(arg)
 end);
 
 InstallGlobalFunction(DIGRAPHS_Clique,
-function(arg)
+function(arg...)
   local maximal, D, include, exclude, size, out, try, include_copy, v;
 
   maximal := arg[1];
@@ -369,7 +369,7 @@ end);
 # Cliques orbit representatives
 
 InstallGlobalFunction(DigraphCliquesReps,
-function(arg)
+function(arg...)
   local D, include, exclude, limit, size;
 
   if IsEmpty(arg) then
@@ -412,7 +412,7 @@ InstallMethod(DigraphCliquesAttr, "for a digraph", [IsDigraph],
 DigraphCliques);
 
 InstallGlobalFunction(DigraphCliques,
-function(arg)
+function(arg...)
   local D, include, exclude, limit, size, out;
 
   if IsEmpty(arg) then
@@ -467,7 +467,7 @@ InstallMethod(DigraphMaximalCliquesRepsAttr, "for a digraph", [IsDigraph],
 DigraphMaximalCliquesReps);
 
 InstallGlobalFunction(DigraphMaximalCliquesReps,
-function(arg)
+function(arg...)
   local D, include, exclude, limit, size, out;
 
   if IsEmpty(arg) then
@@ -521,7 +521,7 @@ InstallMethod(DigraphMaximalCliquesAttr, "for a digraph", [IsDigraph],
 DigraphMaximalCliques);
 
 InstallGlobalFunction(DigraphMaximalCliques,
-function(arg)
+function(arg...)
   local D, include, exclude, limit, size, cliques, sub, G, out, orbits, c;
 
   if IsEmpty(arg) then
@@ -1041,7 +1041,7 @@ function(D, hook, param, lim, inc, exc, max, size, reps, inc_var, exc_var)
       to_try := ListBlist(vtx, try);
     fi;
 
-    if not G = fail then
+    if G <> fail then
       to_try := List(Orbits(G, to_try), x -> x[1]);
     fi;
 
diff --git a/gap/digraph.gi b/gap/digraph.gi
index 488d962ba..21ab2bae8 100644
--- a/gap/digraph.gi
+++ b/gap/digraph.gi
@@ -1221,7 +1221,7 @@ function(filt, digraph, gps, homs)
   local red, n, hom_table, reps, rep, top, doms, starts, degs, max, gens, img,
   start, deg, x, queue, j, k, g, y, hom, edge, i, gen;
 
-  if not filt = IsPartialPermSemigroup then
+  if filt <> IsPartialPermSemigroup then
     TryNextMethod();
   elif not IsJoinSemilatticeDigraph(digraph) then
     if IsMeetSemilatticeDigraph(digraph) then
@@ -1335,7 +1335,7 @@ function(filt, digraph, gps, homs)
         # agrees with the composition we are currently considering.
         if IsBound(img[start]) then
           y := PermList(img{[start .. start + deg - 1]} - start + 1);
-          if not x = y then
+          if x <> y then
             ErrorNoReturn("the homomorphisms given must form a commutative",
                           " diagram,");
           fi;
diff --git a/gap/display.gi b/gap/display.gi
index f55429169..b578f8d60 100644
--- a/gap/display.gi
+++ b/gap/display.gi
@@ -52,11 +52,7 @@ function(str)
       od;
     fi;
   fi;
-  if x = (l - 1) then
-    return true;
-  else
-    return false;
-  fi;
+  return x = (l - 1);
 end);
 
 BindGlobal("DIGRAPHS_GraphvizColorsList", fail);
@@ -266,7 +262,7 @@ if not IsBound(Splash) then  # This function is written by A. Egri-Nagy
              ["xpdf", "xdg-open", "open", "evince", "okular", "gv"]);
 
   BindGlobal("Splash",
-  function(arg)
+  function(arg...)
     local str, opt, path, dir, tdir, file, viewer, type, inn, filetype, out,
           engine;
 
diff --git a/gap/grahom.gi b/gap/grahom.gi
index 1b7d854b6..34a2f393d 100644
--- a/gap/grahom.gi
+++ b/gap/grahom.gi
@@ -11,7 +11,7 @@
 ##
 
 InstallGlobalFunction(GeneratorsOfEndomorphismMonoid,
-function(arg)
+function(arg...)
   local D, limit, colours, G, gens, limit_arg, out;
   if IsEmpty(arg) then
     ErrorNoReturn("at least 1 argument expected, found 0,");
diff --git a/gap/io.gi b/gap/io.gi
index ebf3b0310..383f393b4 100644
--- a/gap/io.gi
+++ b/gap/io.gi
@@ -168,7 +168,7 @@ end;
 ################################################################################
 
 InstallGlobalFunction(IteratorFromDigraphFile,
-function(arg)
+function(arg...)
   local filename, decoder, file, record;
 
   if Length(arg) = 1 then
@@ -314,7 +314,7 @@ function(filename)
 end);
 
 InstallGlobalFunction(DigraphFile,
-function(arg)
+function(arg...)
   local coder, mode, name, file;
 
   # defaults
@@ -374,7 +374,7 @@ function(arg)
 end);
 
 InstallGlobalFunction(ReadDigraphs,
-function(arg)
+function(arg...)
   local nr, decoder, name, file, i, next, out;
 
   # defaults
@@ -455,7 +455,7 @@ function(arg)
 end);
 
 InstallGlobalFunction(WriteDigraphs,
-function(arg)
+function(arg...)
   local name, digraphs, encoder, mode, splitname, compext, g6sum, s6sum, v, e,
         dg6sum, ds6sum, file, D, i;
 
diff --git a/gap/isomorph.gi b/gap/isomorph.gi
index d00bef066..4398878ea 100644
--- a/gap/isomorph.gi
+++ b/gap/isomorph.gi
@@ -296,7 +296,7 @@ InstallMethod(BlissAutomorphismGroup,
 "for a digraph, fail, and edge colouring",
 [IsDigraph, IsBool, IsList],
 function(digraph, vert_colours, edge_colours)
-  if not vert_colours = fail then
+  if vert_colours <> fail then
     TryNextMethod();
   fi;
   return BLISS_DATA(digraph, vert_colours, edge_colours)[1];
diff --git a/gap/oper.gi b/gap/oper.gi
index 8e72d8af7..428fae5d4 100644
--- a/gap/oper.gi
+++ b/gap/oper.gi
@@ -608,7 +608,7 @@ end);
 #############################################################################
 
 InstallGlobalFunction(DIGRAPHS_CombinationOperProcessArgs,
-function(arg)
+function(arg...)
   local copy, i;
   arg := ShallowCopy(arg[1]);
   if IsMutableDigraph(arg[1]) then
@@ -633,7 +633,7 @@ function(arg)
 end);
 
 InstallGlobalFunction(DigraphDisjointUnion,
-function(arg)
+function(arg...)
   local D, offset, n, i, j;
 
   # Allow the possibility of supplying arguments in a list.
@@ -668,7 +668,7 @@ function(arg)
 end);
 
 InstallGlobalFunction(DigraphJoin,
-function(arg)
+function(arg...)
   local D, tot, offset, n, list, i, v;
   # Allow the possibility of supplying arguments in a list.
   if Length(arg) = 1 and IsList(arg[1]) then
@@ -708,7 +708,7 @@ function(arg)
 end);
 
 InstallGlobalFunction(DigraphEdgeUnion,
-function(arg)
+function(arg...)
   local D, n, i, v;
 
   # Allow the possibility of supplying arguments in a list.
@@ -748,7 +748,7 @@ function(arg)
 end);
 
 InstallGlobalFunction(DigraphCartesianProduct,
-function(arg)
+function(arg...)
   local D, n, i, j, proj, m, labs;
 
   # Allow the possibility of supplying arguments in a list.
@@ -794,7 +794,7 @@ function(arg)
 end);
 
 InstallGlobalFunction(DigraphDirectProduct,
-function(arg)
+function(arg...)
   local D, n, i, j, proj, m, labs;
 
   # Allow the possibility of supplying arguments in a list.
diff --git a/gap/utils.gi b/gap/utils.gi
index eba57674b..e978cecfe 100644
--- a/gap/utils.gi
+++ b/gap/utils.gi
@@ -135,7 +135,7 @@ function()
 end);
 
 InstallGlobalFunction(DigraphsTestStandard,
-function(arg)
+function(arg...)
   local opts, dir;
   if Length(arg) = 1 and IsRecord(arg[1]) then
     opts := ShallowCopy(arg[1]);
@@ -164,7 +164,7 @@ function(arg)
 end);
 
 InstallGlobalFunction(DigraphsTestExtreme,
-function(arg)
+function(arg...)
   local file, opts, dir;
   file := Filename(DirectoriesPackageLibrary("digraphs", "digraphs-lib"),
                    "extreme.d6.gz");
@@ -212,7 +212,7 @@ function()
 end);
 
 InstallGlobalFunction(DigraphsTestManualExamples,
-function(arg)
+function(arg...)
   local exlists, indices, omit, oldscr, passed, pad, total, l, sp, bad, s,
   start_time, test, end_time, elapsed, pex, str, j, ex, i;
 
@@ -587,7 +587,7 @@ function(blist)
 end);
 
 InstallGlobalFunction(DError,
-function(arg)
+function(arg...)
   local msg;
   if not (IsString(arg[1]) or IsList(arg[1])) then
     Error("expected a string or a list as the 1st argument");