wip: refactor into crates

crates/tek_core/src/exit.rs

@@ -0,0 +1,20 @@
+pub trait Exit: Send {
+    fn exited (&self) -> bool;
+    fn exit (&mut self);
+    fn boxed (self) -> Box<dyn Exit> where Self: Sized + 'static {
+        Box::new(self)
+    }
+}
+
+#[macro_export] macro_rules! exit {
+    ($T:ty) => {
+        impl Exit for $T {
+            fn exited (&self) -> bool {
+                self.exited
+            }
+            fn exit (&mut self) {
+                self.exited = true
+            }
+        }
+    }
+}