You can now iterate a list

src/list.rs

@@ -14,4 +14,47 @@ impl<'a> List<'a> {
             .rev()
             .fold(Self::Nil, |list, next| Self::Cons(next, Box::new(list)))
     }
+
+    pub fn iter(&self) -> Iter<'_, '_> {
+        Iter(self)
+    }
+}
+
+pub struct Iter<'l, 'v>(&'l List<'v>);
+impl<'l, 'v> Iterator for Iter<'l, 'v> {
+    type Item = &'l Value<'v>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match self.0 {
+            List::Cons(head, rest) => {
+                self.0 = &**rest;
+                Some(head)
+            }
+            List::Nil => None,
+        }
+    }
+}
+
+impl<'a> IntoIterator for List<'a> {
+    type Item = Value<'a>;
+    type IntoIter = IntoIter<'a>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        IntoIter(self)
+    }
+}
+
+pub struct IntoIter<'a>(List<'a>);
+impl<'a> Iterator for IntoIter<'a> {
+    type Item = Value<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match std::mem::take(&mut self.0) {
+            List::Cons(first, mut rest) => {
+                std::mem::swap(&mut self.0, rest.as_mut());
+                Some(first)
+            }
+            List::Nil => None,
+        }
+    }
 }