proper cycle should not have odd length

sagemath · Jan 11, 2020 · aa21ee1 · aa21ee1
1 parent 31cb54b
commit aa21ee1
Showing 1 changed file with 4 additions and 1 deletion.
diff --git a/src/sage/quadratic_forms/binary_qf.py b/src/sage/quadratic_forms/binary_qf.py
@@ -950,7 +950,10 @@ def cycle(self, proper=False):
             # Prop 6.10.5 in Buchmann Vollmer
             C = self.cycle(proper=False)
             if len(C) % 2:
-                return C
+                Cdouble = C + C
+                for i in range(len(C)):
+                    Cdouble[2*i+1] = Cdouble[2*i+1]._Tau()
+                return Cdouble
             else:
                 return C[:1] + [q._Tau() for q in C[1:]]
         if not hasattr(self, '_cycle_list'):