NormalClosure: accept list of normal generators as input

... for the second argument

lib/grp.gi

@@ -2914,6 +2914,12 @@ function(G,U)
   return U;
 end);
 
+InstallOtherMethod( NormalClosure, "generic method for a list of normal generators",
+  IsIdenticalObj, [ IsGroup, IsList ], SUM_FLAGS,
+function(G, list)
+  return NormalClosure(G, Subgroup(G, list));
+end);
+
 #############################################################################
 ##
 #M  NormalIntersection( <G>, <U> )  . . . . . intersection with normal subgrp

tst/testinstall/opers/NormalClosure.tst

@@ -0,0 +1,40 @@
+gap> START_TEST("NormalClosure.tst");
+
+#
+# setup perm groups
+#
+gap> G := SymmetricGroup(4);;
+gap> H := AlternatingGroup(4);;
+
+# normal closure of a subgroup
+gap> G = NormalClosure(G, Group((1,2)));
+true
+gap> H = NormalClosure(G, Group((1,2,3)));
+true
+
+# normal closure of a bunch of generators
+gap> G = NormalClosure(G, [ (1,2) ]);
+true
+gap> H = NormalClosure(G, [ (1,2,3) ]);
+true
+
+#
+# setup fp groups
+#
+gap> G := FreeGroup(2);;
+
+# normal closure of a subgroup
+gap> H := Subgroup(G, [G.1^2, G.2^2, Comm(G.1, G.2)]);;
+gap> Index(G, H);
+infinity
+gap> N := NormalClosure(G, H);;
+gap> Index(G, N);
+4
+
+#
+gap> N := NormalClosure(G, [G.1^2, G.2^2, Comm(G.1, G.2)]);;
+gap> Index(G, N);
+4
+
+#
+gap> STOP_TEST("NormalClosure.tst", 1);