Implemented list.__reversed__

vm/src/obj/objlist.rs

@@ -167,6 +167,14 @@ impl PyListRef {
     fn reverse(self, _vm: &VirtualMachine) {
         self.elements.borrow_mut().reverse();
     }
+    
+    fn reversed(self, _vm: &VirtualMachine) -> PyListReverseIterator {
+        let final_position = self.elements.borrow().len();
+        PyListReverseIterator {
+            position: Cell::new(final_position),
+            list: self,
+        }
+    }
 
     fn getitem(self, needle: PyObjectRef, vm: &VirtualMachine) -> PyResult {
         get_item(
@@ -397,7 +405,7 @@ impl PyListRef {
             .collect();
         vm.ctx.new_list(new_elements)
     }
-
+    
     fn imul(self, counter: isize, _vm: &VirtualMachine) -> Self {
         let new_elements = seq_mul(&self.elements.borrow().as_slice(), counter)
             .cloned()
@@ -405,7 +413,7 @@ impl PyListRef {
         self.elements.replace(new_elements);
         self
     }
-
+    
     fn count(self, needle: PyObjectRef, vm: &VirtualMachine) -> PyResult<usize> {
         let mut count: usize = 0;
         for element in self.elements.borrow().iter() {
@@ -813,6 +821,39 @@ impl PyListIterator {
     }
 }
 
+#[pyclass]
+#[derive(Debug)]
+pub struct PyListReverseIterator {
+    pub position: Cell<usize>,
+    pub list: PyListRef,
+}
+
+impl PyValue for PyListReverseIterator {
+    fn class(vm: &VirtualMachine) -> PyClassRef {
+        vm.ctx.listreverseiterator_type()
+    }
+}
+
+#[pyimpl]
+impl PyListReverseIterator {
+    #[pymethod(name = "__next__")]
+    fn next(&self, vm: &VirtualMachine) -> PyResult {
+        if self.position.get() > 0 {
+            let position: usize = self.position.get() - 1;
+            let ret = self.list.elements.borrow()[position].clone();
+            self.position.set(position);
+            Ok(ret)
+        } else {
+            Err(objiter::new_stop_iteration(vm))
+        }
+    }
+
+    #[pymethod(name = "__iter__")]
+    fn iter(zelf: PyRef<Self>, _vm: &VirtualMachine) -> PyRef<Self> {
+        zelf
+    }
+}
+
 #[rustfmt::skip] // to avoid line splitting
 pub fn init(context: &PyContext) {
     let list_type = &context.list_type;
@@ -835,6 +876,7 @@ pub fn init(context: &PyContext) {
         "__getitem__" => context.new_rustfunc(PyListRef::getitem),
         "__iter__" => context.new_rustfunc(PyListRef::iter),
         "__setitem__" => context.new_rustfunc(PyListRef::setitem),
+        "__reversed__" => context.new_rustfunc(PyListRef::reversed),
         "__mul__" => context.new_rustfunc(PyListRef::mul),
         "__imul__" => context.new_rustfunc(PyListRef::imul),
         "__len__" => context.new_rustfunc(PyListRef::len),
@@ -856,4 +898,5 @@ pub fn init(context: &PyContext) {
     });
 
     PyListIterator::extend_class(context, &context.listiterator_type);
+    PyListReverseIterator::extend_class(context, &context.listreverseiterator_type);
 }

vm/src/pyobject.rs

@@ -134,6 +134,7 @@ pub struct PyContext {
     pub false_value: PyIntRef,
     pub list_type: PyClassRef,
     pub listiterator_type: PyClassRef,
+    pub listreverseiterator_type: PyClassRef,
     pub dictkeyiterator_type: PyClassRef,
     pub dictvalueiterator_type: PyClassRef,
     pub dictitemiterator_type: PyClassRef,
@@ -271,6 +272,7 @@ impl PyContext {
         let str_type = create_type("str", &type_type, &object_type);
         let list_type = create_type("list", &type_type, &object_type);
         let listiterator_type = create_type("list_iterator", &type_type, &object_type);
+        let listreverseiterator_type = create_type("list_reverseiterator", &type_type, &object_type);
         let dictkeys_type = create_type("dict_keys", &type_type, &object_type);
         let dictvalues_type = create_type("dict_values", &type_type, &object_type);
         let dictitems_type = create_type("dict_items", &type_type, &object_type);
@@ -337,6 +339,7 @@ impl PyContext {
             staticmethod_type,
             list_type,
             listiterator_type,
+            listreverseiterator_type,
             dictkeys_type,
             dictvalues_type,
             dictitems_type,
@@ -467,6 +470,10 @@ impl PyContext {
     pub fn listiterator_type(&self) -> PyClassRef {
         self.listiterator_type.clone()
     }
+    
+    pub fn listreverseiterator_type(&self) -> PyClassRef {
+        self.listreverseiterator_type.clone()
+    }
 
     pub fn module_type(&self) -> PyClassRef {
         self.module_type.clone()