py: Implement builtin reversed() function.

reversed function now implemented, and works for tuple, list, str, bytes
and user objects with __len__ and __getitem__.

Renamed mp_builtin_len to mp_obj_len to make it publically available (eg
for reversed).

1 files changed, 33 insertions, 0 deletions

diff --git a/tests/basics/builtin_reversed.py b/tests/basics/builtin_reversed.py
new file mode 100644
index 0000000000..c834cba69e
--- /dev/null
+++ b/tests/basics/builtin_reversed.py
@@ -0,0 +1,33 @@
+# test the builtin reverse() function
+
+# list
+print(list(reversed([])))
+print(list(reversed([1])))
+print(list(reversed([1, 2, 3])))
+
+# tuple
+print(list(reversed(())))
+print(list(reversed((1, 2, 3))))
+
+# string
+for c in reversed('ab'):
+    print(c)
+
+# bytes
+for b in reversed(b'1234'):
+    print(b)
+
+# range
+#for i in reversed(range(3)):
+#    print(i)
+
+# user object
+class A:
+    def __init__(self):
+        pass
+    def __len__(self):
+        return 3
+    def __getitem__(self, pos):
+        return pos + 1
+for a in reversed(A()):
+    print(a)