Converted Interner to work with Rc-s

- Interner no longer contains unsafe code
- Tokens now hold a reference to the value they represent directly

This will enable many future improvements

src/systems/stl/state.rs

@@ -0,0 +1,61 @@
+use std::cell::RefCell;
+use std::rc::Rc;
+
+use crate::foreign::cps_box::{const_cps, init_cps, CPSBox};
+use crate::foreign::Atomic;
+use crate::interpreted::ExprInst;
+use crate::interpreter::HandlerTable;
+use crate::systems::codegen::call;
+use crate::{atomic_inert, define_fn, ConstTree, Interner};
+
+#[derive(Debug, Clone)]
+pub struct State(Rc<RefCell<ExprInst>>);
+atomic_inert!(State, "a state");
+
+#[derive(Debug, Clone)]
+struct NewStateCmd;
+
+#[derive(Debug, Clone)]
+struct SetStateCmd(State);
+
+#[derive(Debug, Clone)]
+struct GetStateCmd(State);
+
+define_fn! { SetState = |x| Ok(init_cps(2, SetStateCmd(x.try_into()?))) }
+define_fn! { GetState = |x| Ok(init_cps(2, GetStateCmd(x.try_into()?))) }
+
+fn new_state_handler<E>(cmd: &CPSBox<NewStateCmd>) -> Result<ExprInst, E> {
+  let (_, default, handler) = cmd.unpack2();
+  let state = State(Rc::new(RefCell::new(default.clone())));
+  Ok(call(handler.clone(), [state.atom_exi()]).wrap())
+}
+
+fn set_state_handler<E>(cmd: &CPSBox<SetStateCmd>) -> Result<ExprInst, E> {
+  let (SetStateCmd(state), value, handler) = cmd.unpack2();
+  *state.0.as_ref().borrow_mut() = value.clone();
+  Ok(handler.clone())
+}
+
+fn get_state_handler<E>(cmd: &CPSBox<GetStateCmd>) -> Result<ExprInst, E> {
+  let (GetStateCmd(state), handler) = cmd.unpack1();
+  Ok(call(handler.clone(), [state.0.as_ref().borrow().clone()]).wrap())
+}
+
+pub fn state_handlers() -> HandlerTable<'static> {
+  let mut handlers = HandlerTable::new();
+  handlers.register(new_state_handler);
+  handlers.register(get_state_handler);
+  handlers.register(set_state_handler);
+  handlers
+}
+
+pub fn state_lib(i: &Interner) -> ConstTree {
+  ConstTree::namespace(
+    [i.i("state")],
+    ConstTree::tree([
+      (i.i("new_state"), const_cps(2, NewStateCmd)),
+      (i.i("get_state"), ConstTree::xfn(GetState)),
+      (i.i("set_state"), ConstTree::xfn(SetState)),
+    ]),
+  )
+}