Add base branch logic

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/obj/int.rs

@@ -15,6 +15,12 @@ static INT_ATTRS: LazyLock<AttrsPtr> = LazyLock::new(|| {
 
             BuiltinFunResult::Return(Some(ObjPtr::new(Str::new(obj.value().to_string()))))
         }),
+        "__bool__" => builtin_fun_ptr!("__bool__", |_vm, args, _state| {
+            let arg_any = &args[0].as_any();
+            let obj = arg_any.downcast_ref::<Int>().expect("Int.__bool__ did not receive Int?");
+            let result = ObjPtr::clone(&BOOL_INSTS[obj.is_truthy() as usize]);
+            BuiltinFunResult::Return(Some(result))
+        }),
     }
 });
 
@@ -44,6 +50,10 @@ impl Obj for Int {
     fn as_any(&self) -> &(dyn Any + 'static) {
         self
     }
+
+    fn is_truthy(&self) -> bool {
+        self.value() != 0
+    }
 }
 
 impl ToString for Int {