Implement tuple.index().

py/objtuple.c

@@ -153,6 +153,18 @@ static mp_obj_t tuple_getiter(mp_obj_t o_in) {
     return mp_obj_new_tuple_iterator(o_in, 0);
 }
 
+static mp_obj_t tuple_index(uint n_args, const mp_obj_t *args) {
+    assert(MP_OBJ_IS_TYPE(args[0], &tuple_type));
+    mp_obj_tuple_t *self = args[0];
+    return mp_seq_index_obj(self->items, self->len, n_args, args);
+}
+static MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(tuple_index_obj, 2, 4, tuple_index);
+
+static const mp_method_t tuple_type_methods[] = {
+    { "index", &tuple_index_obj },
+    { NULL, NULL }, // end-of-list sentinel
+};
+
 const mp_obj_type_t tuple_type = {
     { &mp_const_type },
     "tuple",
@@ -161,6 +173,7 @@ const mp_obj_type_t tuple_type = {
     .unary_op = tuple_unary_op,
     .binary_op = tuple_binary_op,
     .getiter = tuple_getiter,
+    .methods = tuple_type_methods,
 };
 
 // the zero-length tuple

py/sequence.c

@@ -156,9 +156,10 @@ mp_obj_t mp_seq_index_obj(const mp_obj_t *items, uint len, uint n_args, const mp
     }
 
     for (uint i = start; i < stop; i++) {
-         if (mp_obj_equal(items[i], value)) {
+        if (mp_obj_equal(items[i], value)) {
-              return mp_obj_new_int_from_uint(i);
+            // Common sense says this cannot overflow small int
-         }
+            return MP_OBJ_NEW_SMALL_INT(i);
+        }
     }
 
     nlr_jump(mp_obj_new_exception_msg(MP_QSTR_ValueError, "object not in sequence"));

tests/basics/tuple_index.py

@@ -0,0 +1,24 @@
+a = (1, 2, 3)
+print(a.index(1))
+print(a.index(2))
+print(a.index(3))
+print(a.index(3, 2))
+try:
+    print(a.index(3, 2, 2))
+except ValueError:
+    print("Raised ValueError")
+else:
+    print("Did not raise ValueError")
+
+a = a + a
+b = (0, 0, a)
+print(a.index(2))
+print(b.index(a))
+print(a.index(2, 2))
+
+try:
+    a.index(2, 2, 2)
+except ValueError:
+    print("Raised ValueError")
+else:
+    print("Did not raise ValueError")