Generic mutation scheduling system

IO adapted to use it
Also, Atoms can now dispatch type-erased requests

src/foreign/atom.rs

@@ -34,6 +34,12 @@ pub trait Atomic: Any + Debug + DynClone
 where
   Self: 'static,
 {
+  /// A fully type-erased interface to issue a command to the unknown type
+  /// and see if it supports it
+  fn request(&self, _request: Box<dyn Any>) -> Option<Box<dyn Any>> {
+    None
+  }
+
   /// Casts this value to [Any] so that its original value can be salvaged
   /// during introspection by other external code. There is no other way to
   /// interact with values of unknown types at the moment.

src/foreign/cps_box.rs

@@ -4,11 +4,11 @@ use std::fmt::Debug;
 
 use trait_set::trait_set;
 
-use super::{Atomic, AtomicResult, AtomicReturn, ExternFn, XfnResult};
+use super::{Atomic, ExternFn, XfnResult};
 use crate::interpreted::{Clause, ExprInst};
 use crate::interpreter::{Context, HandlerRes};
-use crate::utils::pushed::pushed_ref;
-use crate::{atomic_defaults, ConstTree};
+use crate::utils::pure_push::pushed_ref;
+use crate::{ConstTree, atomic_inert};
 
 trait_set! {
   /// A "well behaved" type that can be used as payload in a CPS box
@@ -93,16 +93,7 @@ impl<T: CPSPayload> CPSBox<T> {
   }
 }
 
-impl<T: CPSPayload> Atomic for CPSBox<T> {
-  atomic_defaults!();
-  fn run(&self, ctx: Context) -> AtomicResult {
-    Ok(AtomicReturn {
-      clause: self.clone().atom_cls(),
-      gas: ctx.gas,
-      inert: true,
-    })
-  }
-}
+atomic_inert!(CPSBox(T:(CPSPayload)), typestr = "a CPS box");
 
 /// Like [init_cps] but wrapped in a [ConstTree] for init-time usage
 pub fn const_cps<T: CPSPayload>(argc: usize, payload: T) -> ConstTree {