From d230fd817195acd918ca50c29ba52439020777db Mon Sep 17 00:00:00 2001
From: Max Horn <max@quendi.de>
Date: Tue, 23 Jan 2018 12:35:49 +0100
Subject: [PATCH] Fix one IsPNilpotent method, and add some tests

---
 lib/grp.gi                                  |  2 +-
 tst/testinstall/opers/IsPNilpotent.tst      | 15 ++++++++++
 tst/testinstall/opers/SimpleGroup.tst       | 28 +++++++++++++++++
 tst/testinstall/opers/SubdirectProducts.tst | 33 +++++++++++++++++++++
 4 files changed, 77 insertions(+), 1 deletion(-)
 create mode 100644 tst/testinstall/opers/IsPNilpotent.tst
 create mode 100644 tst/testinstall/opers/SimpleGroup.tst
 create mode 100644 tst/testinstall/opers/SubdirectProducts.tst

diff --git a/lib/grp.gi b/lib/grp.gi
index 2a673a869d..5d6a2aa22e 100644
--- a/lib/grp.gi
+++ b/lib/grp.gi
@@ -2622,7 +2622,7 @@ InstallMethod( IsPNilpotentOp,
     local primes, S;
 
     primes:= PrimeDivisors( Size( G ) );
-    RemoveSet( primes, p );
+    primes:= Filtered(primes, q -> q <> p );
     S:= HallSubgroup( G, primes );
 
     return S <> fail and IsNormal( G, S );
diff --git a/tst/testinstall/opers/IsPNilpotent.tst b/tst/testinstall/opers/IsPNilpotent.tst
new file mode 100644
index 0000000000..9511f8ae8c
--- /dev/null
+++ b/tst/testinstall/opers/IsPNilpotent.tst
@@ -0,0 +1,15 @@
+gap> START_TEST("IsPNilpotent.tst");
+
+#
+gap> G:=SymmetricGroup(3);;
+gap> List([2,3,5], p -> IsPNilpotent(G,p));
+[ true, false, true ]
+
+#
+gap> G:=SymmetricGroup(3);;
+gap> SpecialPcgs(G);;
+gap> List([2,3,5], p -> IsPNilpotent(G,p));
+[ true, false, true ]
+
+#
+gap> STOP_TEST("IsPNilpotent.tst", 10000);
diff --git a/tst/testinstall/opers/SimpleGroup.tst b/tst/testinstall/opers/SimpleGroup.tst
new file mode 100644
index 0000000000..9bc119eb67
--- /dev/null
+++ b/tst/testinstall/opers/SimpleGroup.tst
@@ -0,0 +1,28 @@
+gap> START_TEST("SimpleGroup.tst");
+
+#
+gap> SimpleGroup("Sz(8)");
+Sz(8)
+gap> SimpleGroup("Suzuki(32)");
+Sz(32)
+gap> SimpleGroup("Suz(8)");
+Sz(8)
+gap> SimpleGroup("Sz(9)");
+Error, Illegal Parameter for Suzuki groups
+gap> SimpleGroup("Suz(16)");
+Error, Illegal Parameter for Suzuki groups
+
+#
+gap> SimpleGroup("R(27)");
+Ree(27)
+gap> SimpleGroup("Ree(27)");
+Ree(27)
+gap> SimpleGroup("2G(243)");
+Ree(243)
+gap> SimpleGroup("Ree(9)");
+Error, Illegal Parameter for Ree groups
+gap> SimpleGroup("Ree(16)");
+Error, Illegal Parameter for Ree groups
+
+#
+gap> STOP_TEST("SimpleGroup.tst", 10000);
diff --git a/tst/testinstall/opers/SubdirectProducts.tst b/tst/testinstall/opers/SubdirectProducts.tst
new file mode 100644
index 0000000000..71b5f1fd42
--- /dev/null
+++ b/tst/testinstall/opers/SubdirectProducts.tst
@@ -0,0 +1,33 @@
+gap> START_TEST("SubdirectProducts.tst");
+gap> G := SymmetricGroup(3);;
+gap> H := SymmetricGroup(4);;
+gap> A := CyclicGroup(6);;
+
+#
+gap> Set(SubdirectProducts(G, G), IdGroup);
+[ [ 6, 1 ], [ 18, 4 ], [ 36, 10 ] ]
+gap> Set(SubdirectProducts(H, H), IdGroup);
+[ [ 24, 12 ], [ 96, 227 ], [ 288, 1026 ], [ 576, 8653 ] ]
+gap> Set(SubdirectProducts(A, A), IdGroup);
+[ [ 6, 2 ], [ 12, 5 ], [ 18, 5 ], [ 36, 14 ] ]
+
+#
+gap> Set(SubdirectProducts(G, H), IdGroup);
+[ [ 24, 12 ], [ 72, 43 ], [ 144, 183 ] ]
+gap> Set(SubdirectProducts(H, G), IdGroup);
+[ [ 24, 12 ], [ 72, 43 ], [ 144, 183 ] ]
+
+#
+gap> Set(SubdirectProducts(G, A), IdGroup);
+[ [ 18, 3 ], [ 36, 12 ] ]
+gap> Set(SubdirectProducts(A, G), IdGroup);
+[ [ 18, 3 ], [ 36, 12 ] ]
+
+#
+gap> Set(SubdirectProducts(H, A), IdGroup);
+[ [ 72, 42 ], [ 144, 188 ] ]
+gap> Set(SubdirectProducts(A, H), IdGroup);
+[ [ 72, 42 ], [ 144, 188 ] ]
+
+#
+gap> STOP_TEST("SubdirectProducts.tst", 10000);