Re: [sage-devel] "!=" is different from "not ==" for permutation groups

['Reimundo Heluani' via sage-devel]

On Apr 30, Vincent Delecroix wrote:

Your fix looks good Reimundo. Could you open a ticket and post the
number in this thread?

Sure, it's here:
https://trac.sagemath.org/ticket/29624#ticket

Cheers, R.

Vincent

Le 29/04/2020 à 19:54, 'Reimundo Heluani' via sage-devel a écrit :

On Apr 29, Dennis Epple wrote:

Hello,

"!=" does not seem to work for permutation groups.

sage: G = SymmetricGroup(2)
sage: H = PermutationGroup([(1,2)])
sage: not G == H
False
sage: G != H
True

It seems it's in the richcmp method of PermutationGroup_generic. The following diff fixes this particular instance, but someone may want to do this better:

index 8512b01122..fd7f1d9777 100644
--- a/src/sage/groups/perm_gps/permgroup.py
+++ b/src/sage/groups/perm_gps/permgroup.py

 from sage.categories.all import FiniteEnumeratedSets
 from sage.groups.conjugacy_classes import ConjugacyClassGAP
 from sage.structure.richcmp import (richcmp_method,
-                                    richcmp, rich_to_bool, op_EQ)
+                                    richcmp, rich_to_bool, op_EQ, op_NE)


 def load_hap():
@@ -701,7 +701,7 @@ class PermutationGroup_generic(FiniteGroup):

         gSelf = self._libgap_()
         gRight = right._libgap_()
-        if op == op_EQ:
+        if op in [op_EQ,op_NE]:
             return gSelf._richcmp_(gRight, op)

         if gSelf.IsSubgroup(gRight):

diff --git a/src/sage/groups/perm_gps/permgroup.py b/src/sage/groups/perm_gps/permgroup.py @@ -158,7 +158,7 @@ from sage.sets.finite_enumerated_set import FiniteEnumeratedSet

sage: G = PermutationGroup([(1,2)])
sage: H = PermutationGroup([(1,2)])
sage: not G == H
False
sage: G != H
True
sage: G = SymmetricGroup(2)
sage: H = SymmetricGroup(2)
sage: not G == H
False
sage: G != H
False

SageMath version 9.0
Python 3.7.3.

Best regards,
Dennis

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