1 files changed, 26 insertions, 3 deletions
diff --git a/ocaml/lib/noun.ml b/ocaml/lib/noun.ml
index c59ec80..9be65b7 100644
--- a/ocaml/lib/noun.ml
+++ b/ocaml/lib/noun.ml
@@ -40,16 +40,39 @@ let tail = function
     - 2 is head, 3 is tail
     - For n > 1: if even, go left; if odd, go right
 *)
+let slot_debug = ref false
+
 let rec slot n noun =
-  if Z.equal n Z.one then
+  let debug = !slot_debug && (Z.equal n (Z.of_int 2) || Z.equal n (Z.of_int 3)) in
+  if debug then
+    Printf.eprintf "[SLOT-DEBUG] slot(%s, noun)\n%!" (Z.to_string n);
+
+  if Z.equal n Z.one then begin
+    if debug then Printf.eprintf "[SLOT-DEBUG] slot(%s) = identity\n%!" (Z.to_string n);
     noun
+  end
   else if Z.equal n Z.zero then
     raise Exit
-  else
+  else begin
     let bit = Z.testbit n 0 in  (* Check if odd *)
     let parent = Z.shift_right n 1 in
+    if debug then
+      Printf.eprintf "[SLOT-DEBUG] slot(%s): bit=%b parent=%s\n%!"
+        (Z.to_string n) bit (Z.to_string parent);
     let sub = slot parent noun in
-    if bit then tail sub else head sub
+    let result = if bit then tail sub else head sub in
+    if debug then begin
+      Printf.eprintf "[SLOT-DEBUG] slot(%s): taking %s, result is %s\n%!"
+        (Z.to_string n) (if bit then "tail" else "head")
+        (if is_cell result then
+          let h = head result in
+          if is_atom h then
+            (match h with Atom z -> "cell[" ^ Z.to_string z ^ " ...]" | _ -> "cell[? ...]")
+          else "cell[cell ...]"
+        else "atom")
+    end;
+    result
+  end
 
 (** Equality test for nouns *)
 let rec equal a b =