support.bits: fix __getitem__ for negative keys

Fixes #244
GlasgowEmbedded · Dec 10, 2020 · 047ed15 · 047ed15
1 parent 13177a5
commit 047ed15
Showing 1 changed file with 4 additions and 1 deletion.
diff --git a/software/glasgow/support/bits.py b/software/glasgow/support/bits.py
@@ -114,7 +114,7 @@ def __repr__(self):
     def __getitem__(self, key):
         if isinstance(key, int):
             if key < 0:
-                return (self._int_ >> (self._len_ - key)) & 1
+                return (self._int_ >> (self._len_ + key)) & 1
             else:
                 return (self._int_ >> key) & 1
         if isinstance(key, slice):
@@ -312,6 +312,9 @@ def test_getitem_int(self):
         self.assertEqual(some[0], 1)
         self.assertEqual(some[2], 0)
         self.assertEqual(some[5], 0)
+        self.assertEqual(some[-1], 1)
+        self.assertEqual(some[-2], 0)
+        self.assertEqual(some[-5], 1)
 
     def test_getitem_slice(self):
         some = bits("10001001011")