Rule execution now runs, no tests tho

src/utils/mod.rs

@@ -2,11 +2,33 @@ mod cache;
 mod substack;
 mod side;
 mod merge_sorted;
-mod sorted_pairs;
 mod unwrap_or_continue;
+pub mod iter;
 pub use cache::Cache;
+use mappable_rc::Mrc;
 pub use substack::Stackframe;
 pub use side::Side;
 pub use merge_sorted::merge_sorted;
+pub use iter::BoxedIter;
 
-pub type BoxedIter<'a, T> = Box<dyn Iterator<Item = T> + 'a>;
+pub fn mrc_derive<T: ?Sized, P, U: ?Sized>(m: &Mrc<T>, p: P) -> Mrc<U>
+where P: for<'a> FnOnce(&'a T) -> &'a U {
+    Mrc::map(Mrc::clone(m), p)
+}
+
+pub fn mrc_try_derive<T: ?Sized, P, U: ?Sized>(m: &Mrc<T>, p: P) -> Option<Mrc<U>>
+where P: for<'a> FnOnce(&'a T) -> Option<&'a U> {
+    Mrc::try_map(Mrc::clone(m), p).ok()
+}
+
+pub fn to_mrc_slice<T>(v: Vec<T>) -> Mrc<[T]> {
+    Mrc::map(Mrc::new(v), |v| v.as_slice())
+}
+
+pub fn collect_to_mrc<I>(iter: I) -> Mrc<[I::Item]> where I: Iterator {
+    to_mrc_slice(iter.collect())
+}
+
+pub fn mrc_derive_slice<T>(mv: &Mrc<Vec<T>>) -> Mrc<[T]> {
+    mrc_derive(mv, |v| v.as_slice())
+}