Fix WreathProductElementList to not modify its list argument (#5801)

Otherwise the list representation from the input gets replaced with the wreath product element outside of the scope.
gap-system · Sep 23, 2024 · 2a7cf16 · 2a7cf16
1 parent 5c79e69
commit 2a7cf16
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diff --git a/lib/gprd.gi b/lib/gprd.gi
@@ -959,7 +959,7 @@ end);
 InstallMethod( WreathProductElementListNC, "generic wreath product", true,
  [ HasWreathProductInfo, IsList ], 0,
 function(G, list)
-  return Objectify(FamilyObj(One(G))!.defaultType, StructuralCopy(list));
+  return Objectify(FamilyObj(One(G))!.defaultType, ShallowCopy(list));
 end);
 
 #############################################################################

diff --git a/tst/testinstall/opers/ListWreathProductElement.tst b/tst/testinstall/opers/ListWreathProductElement.tst
@@ -241,5 +241,21 @@ gap> list := ListWreathProductElement(G, x);;
 gap> x = WreathProductElementList(G, list);
 true
 
+#
+# Generic Wreath Product : Bugfix for immutable lists
+#
+
+#
+gap> K := FreeGroup("x", "y");;
+gap> x := K.1;;
+gap> y := K.2;;
+gap> H := SymmetricGroup(3);;
+gap> W := WreathProduct(K, H);;
+gap> l := [x*y, x, y, (1,2,3)];;
+gap> MakeImmutable(l);;
+gap> w := WreathProductElementList(W, l);;
+gap> l = [x*y, x, y, (1,2,3)];
+true
+
 #
 gap> STOP_TEST("ListWreathProductElement.tst", 1);