Preparation for sharing

- rustfmt
- clippy
- comments
- README

src/foreign_macros/externfn_impl.rs

@@ -1,41 +1,47 @@
 #[allow(unused)] // for the doc comments
-use crate::{atomic_impl, atomic_redirect};
-#[allow(unused)] // for the doc comments
-use crate::representations::Primitive;
-#[allow(unused)] // for the doc comments
-use crate::foreign::{Atomic, ExternFn};
-#[allow(unused)] // for the doc comments
 use std::any::Any;
 #[allow(unused)] // for the doc comments
+use std::fmt::Debug;
+#[allow(unused)] // for the doc comments
 use std::hash::Hash;
+
 #[allow(unused)] // for the doc comments
 use dyn_clone::DynClone;
-#[allow(unused)] // for the doc comments
-use std::fmt::Debug;
 
-/// Implement [ExternFn] with a closure that produces an [Atomic] from a reference to self
-/// and a closure. This can be used in conjunction with [atomic_impl] and [atomic_redirect]
-/// to normalize the argument automatically before using it.
+#[allow(unused)] // for the doc comments
+use crate::foreign::{Atomic, ExternFn};
+#[allow(unused)] // for the doc comments
+use crate::representations::Primitive;
+#[allow(unused)] // for the doc comments
+use crate::{atomic_impl, atomic_redirect};
+
+/// Implement [ExternFn] with a closure that produces an [Atomic] from a
+/// reference to self and a closure. This can be used in conjunction with
+/// [atomic_impl] and [atomic_redirect] to normalize the argument automatically
+/// before using it.
 #[macro_export]
 macro_rules! externfn_impl {
   ($typ:ident, $next_atomic:expr) => {
     impl $crate::foreign::ExternFn for $typ {
-      fn name(&self) -> &str {stringify!($typ)}
-      fn apply(&self,
+      fn name(&self) -> &str {
+        stringify!($typ)
+      }
+      fn apply(
+        &self,
         arg: $crate::foreign::RcExpr,
-        _ctx: $crate::interpreter::Context
+        _ctx: $crate::interpreter::Context,
       ) -> $crate::foreign::XfnResult {
-        match ($next_atomic)(self, arg) { // ? casts the result but we want to strictly forward it
-          Ok(r) => Ok(
-            $crate::representations::interpreted::Clause::P(
-              $crate::representations::Primitive::Atom(
-                $crate::foreign::Atom::new(r)
-              )
-            )
-          ),
-          Err(e) => Err(e)
+        let closure = $next_atomic;
+        match closure(self, arg) {
+          // ? casts the result but we want to strictly forward it
+          Ok(r) => Ok($crate::representations::interpreted::Clause::P(
+            $crate::representations::Primitive::Atom(
+              $crate::foreign::Atom::new(r),
+            ),
+          )),
+          Err(e) => Err(e),
         }
       }
     }
   };
-}
+}