Fix Extensions for nonsolvable group and trivial cohomology (#5908)

gap-system · Jan 20, 2025 · 2f5918d · 2f5918d
1 parent fad9aad
commit 2f5918d
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diff --git a/lib/twocohom.gi b/lib/twocohom.gi
@@ -2026,7 +2026,7 @@ InstallOtherMethod(Extensions,"generic method for finite groups",
 function(G,M)
 local coh;
   coh:=TwoCohomologyGeneric(G,M);
-  return List(Elements(VectorSpace(coh.module.field,coh.cohomology)),
+  return List(Elements(VectorSpace(coh.module.field,coh.cohomology,coh.zero)),
     x->FpGroupCocycle(coh,x,true:normalform));
 end);
 

diff --git a/tst/teststandard/twocohom.tst b/tst/teststandard/twocohom.tst
@@ -58,6 +58,9 @@ gap> cp:=CompatiblePairs(g,mo);
 <group of size 240 with 4 generators>
 gap> Length(ExtensionRepresentatives(g,mo,cp));
 2
+gap> mo:= TrivialGModule( g, GF(3) );;
+gap> Length( Extensions( g, mo ) );
+1
 
 # New code for Pc groups
 gap> g:=AbelianGroup([2,2]);;