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, 10 insertions, 0 deletions

diff --git a/py/obj.c b/py/obj.c
index 04716454d..d8fccfb7b 100644
--- a/py/obj.c
+++ b/py/obj.c
@@ -360,6 +360,16 @@ uint mp_get_index(const mp_obj_type_t *type, mp_uint_t len, mp_obj_t index, bool
     return i;
 }
 
+// will raise a TypeError if object has no length
+mp_obj_t mp_obj_len(mp_obj_t o_in) {
+    mp_obj_t len = mp_obj_len_maybe(o_in);
+    if (len == MP_OBJ_NULL) {
+        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_TypeError, "object of type '%s' has no len()", mp_obj_get_type_str(o_in)));
+    } else {
+        return len;
+    }
+}
+
 // may return MP_OBJ_NULL
 mp_obj_t mp_obj_len_maybe(mp_obj_t o_in) {
     if (