Implement slicing for lists.

py/obj.h

@@ -396,3 +396,4 @@ typedef struct _mp_obj_classmethod_t {
 // sequence helpers
 void mp_seq_multiply(const void *items, uint item_sz, uint len, uint times, void *dest);
 bool m_seq_get_fast_slice_indexes(machine_uint_t len, mp_obj_t slice, machine_uint_t *begin, machine_uint_t *end);
+#define m_seq_copy(dest, src, len, item_sz) memcpy(dest, src, len * sizeof(item_sz))

py/objlist.c

@@ -136,7 +136,15 @@ static mp_obj_t list_binary_op(int op, mp_obj_t lhs, mp_obj_t rhs) {
     switch (op) {
         case RT_BINARY_OP_SUBSCR:
         {
-            // list load
+#if MICROPY_ENABLE_SLICE
+            if (MP_OBJ_IS_TYPE(rhs, &slice_type)) {
+                machine_uint_t start, stop;
+                assert(m_seq_get_fast_slice_indexes(o->len, rhs, &start, &stop));
+                mp_obj_list_t *res = list_new(stop - start);
+                m_seq_copy(res->items, o->items + start, res->len, mp_obj_t);
+                return res;
+            }
+#endif
             uint index = mp_get_index(o->base.type, o->len, rhs);
             return o->items[index];
         }

tests/basics/list1.py

@@ -16,3 +16,7 @@ print(x)
 
 x += [2, 1]
 print(x)
+
+print(x[1:])
+print(x[:-1])
+print(x[2:3])