diff --git a/src/builtins.rs b/src/builtins.rs
index 5d5beb4..75ab905 100644
--- a/src/builtins.rs
+++ b/src/builtins.rs
@@ -45,8 +45,8 @@ pub(crate) fn println(vm: &mut Vm, state: FunctionState) -> FunctionResult {
             let method_type = vm.builtins().get("Method").unwrap().clone();
             let to_repr = obj
                 .borrow_mut()
-                .get_attr_lazy(obj.clone(), method_type, "to_repr")
-                .expect("no to_repr");
+                .get_attr_lazy(obj.clone(), method_type, "to_str")
+                .expect("no to_str");
             to_repr.borrow().call(vm, 0);
             FunctionResult::Yield(0)
         }
@@ -65,8 +65,8 @@ pub(crate) fn print(vm: &mut Vm, state: FunctionState) -> FunctionResult {
             let method_type = vm.builtins().get("Method").unwrap().clone();
             let to_repr = obj
                 .borrow_mut()
-                .get_attr_lazy(obj.clone(), method_type, "to_repr")
-                .expect("no to_repr");
+                .get_attr_lazy(obj.clone(), method_type, "to_str")
+                .expect("no to_str");
             to_repr.borrow().call(vm, 0);
             FunctionResult::Yield(0)
         }
@@ -87,6 +87,23 @@ impl BaseObjInst {
     // Common functions
     //
 
+    pub(crate) fn to_str(vm: &mut Vm, state: FunctionState) -> FunctionResult {
+        match state {
+            FunctionState::Begin => {
+                let this = vm.frame_stack()[0].clone();
+                let method_type = vm.builtins().get("Method").unwrap().clone();
+                let to_repr = this
+                    .borrow_mut()
+                    .get_attr_lazy(this.clone(), method_type, "to_repr")
+                    .expect("no to_repr");
+                to_repr.borrow().call(vm, 0);
+                FunctionResult::Yield(0)
+            }
+            FunctionState::Resume(0) => FunctionResult::Return,
+            _ => unreachable!(),
+        }
+    }
+
     pub(crate) fn to_repr(vm: &mut Vm, _state: FunctionState) -> FunctionResult {
         let str_value = format!("{}", vm.frame_stack()[0].borrow());
         vm.create_str(str_value).into()
@@ -200,7 +217,7 @@ impl StrInst {
             with_obj_downcast(vm.frame_stack()[0].clone(), |str_inst: &StrInst| {
                 str_inst.str_value().as_str().escape_default().collect()
             });
-        vm.create_str(escaped).into()
+        vm.create_str(format!("'{}'", escaped)).into()
     }
 
     pub(crate) fn len(vm: &mut Vm, _state: FunctionState) -> FunctionResult {
diff --git a/src/obj.rs b/src/obj.rs
index 1f38867..a6422f3 100644
--- a/src/obj.rs
+++ b/src/obj.rs
@@ -20,6 +20,8 @@ pub type Ptr<T> = Gc<GcCell<T>>;
 pub type ObjP = Ptr<dyn Obj>;
 pub type Attrs = HashMap<String, ObjP>;
 
+// TODO obj::with_obj_downcast - optimize downcasts of "known" types with an unchecked downcast
+
 /// Downcast an object pointer to a concrete type, and do something with that object.
 pub fn with_obj_downcast<T, Out>(ptr: ObjP, closure: impl FnOnce(&T) -> Out) -> Out
 where
@@ -116,7 +118,7 @@ pub fn init_types(builtins: &mut HashMap<String, ObjP>) {
         // type definitions
         Type {
             // Method conversion
-            to_str => builtins.create_builtin_function("to_str", BaseObjInst::to_repr, 1),
+            to_str => builtins.create_builtin_function("to_str", BaseObjInst::to_str, 1),
             to_repr => builtins.create_builtin_function("to_repr", BaseObjInst::to_repr, 1),
             to_bool => builtins.create_builtin_function("to_bool", BaseObjInst::to_bool, 1),
             len => builtins.create_builtin_function("len", BaseObjInst::not_implemented_un, 1),
@@ -145,6 +147,7 @@ pub fn init_types(builtins: &mut HashMap<String, ObjP>) {
             // Operators
             __add__ => builtins.create_builtin_function("__add__", StrInst::add, 2),
             __mul__ => builtins.create_builtin_function("__mul__", StrInst::mul, 2),
+            // .lower, .upper, .slice, etc
         },
         Int {
             // Operators
@@ -156,8 +159,8 @@ pub fn init_types(builtins: &mut HashMap<String, ObjP>) {
             __ge__ => builtins.create_builtin_function("__ge__", IntInst::ge, 2),
             __lt__ => builtins.create_builtin_function("__lt__", IntInst::lt, 2),
             __le__ => builtins.create_builtin_function("__le__", IntInst::le, 2),
-            __pos__ => builtins.create_builtin_function("__pos__", IntInst::pos, 2),
-            __neg__ => builtins.create_builtin_function("__neg__", IntInst::neg, 2),
+            __pos__ => builtins.create_builtin_function("__pos__", IntInst::pos, 1),
+            __neg__ => builtins.create_builtin_function("__neg__", IntInst::neg, 1),
         },
         Float { },
         Bool { },