From cbf8e29a84f9d23f775a8e0c3bc395b1ab55352a Mon Sep 17 00:00:00 2001
From: Bram van den Heuvel <bram.vdh1999@gmail.com>
Date: Fri, 10 Jul 2026 00:03:13 +0200
Subject: [PATCH] Generalize normalize function

---
 checker/terms.py | 76 ++++++++++++++++++++++++++++++------------------
 1 file changed, 48 insertions(+), 28 deletions(-)

diff --git a/checker/terms.py b/checker/terms.py
index 09642ee..4257bef 100644
--- a/checker/terms.py
+++ b/checker/terms.py
@@ -29,48 +29,63 @@ def normalize(term : Term) -> Term:
         Create a normalization function. This function simplifies functions as
         much as possible.
     """
-
     def norm_iter(term : Term) -> Term:
         """
-            Normalize a single term. Trust that all children values have
-            already been normalized, or that they will be normalized later on.
-
-            :param term: The term to normalize.
-            :type term: Term
-            :return: A normalized version of the term.
-            :rtype: Term
+            Normalize a single term. Use both the standard normalization scheme
         """
-        match term:
-            case App():
-                match term.f:
-                    case Lambda():
-                        return term.f.substitute(value=norm_iter(term.x))
-                    
-                    case _:
-                        return term
-            
-            case Const():
-                return _known_consts.get(term.name, term)
-            
-            case Lambda():
-                return term
-            
-            case Var():
-                return term
+        for func in _known_norms:
+            term = func(term)
         
-            case Term():
-                return term
+        return term
 
     return traverse(f=norm_iter, term=term)
 
 def register_known_const(name : str, value : Term) -> None:
     _known_consts[name] = value
 
+def register_known_norm(func : Callable[[Term], Term]) -> None:
+    _known_norms.append(func)
+
+def std_norm_iter(term : Term) -> Term:
+    """
+        Normalize a single term. Trust that all children values have
+        already been normalized, or that they will be normalized later on.
+
+        :param term: The term to normalize.
+        :type term: Term
+        :return: A normalized version of the term.
+        :rtype: Term
+    """
+    match term:
+        case App():
+            match term.f:
+                case Lambda():
+                    return term.f.substitute(value=term.x)
+                
+                case _:
+                    return term
+        
+        case Const():
+            return _known_consts.get(term.name, term)
+        
+        case Lambda():
+            return term
+        
+        case Var():
+            return term
+    
+        case Term():
+            return term
+_known_norms.append(std_norm_iter)
+
 def traverse(f : Callable[[Term], Term], term : Term) -> Term:
     """
         Traverse through the tree back-and-forth, aiming to run the given
         function as thoroughly as possible to manipulate the term tree.
 
+        The function quits once no more operations are created.
+        **WARNING:** This means the tree might traverse forever.
+
         :param f: The traversal function that replaces terms.
         :type f: Callable[[Term], Term]
         :param term: The term to traverse.
@@ -78,7 +93,12 @@ def traverse(f : Callable[[Term], Term], term : Term) -> Term:
         :return: The result of the traversed term.
         :rtype: Term
     """
-    return traverse_bottom_up(f=f, term=traverse_top_down(f=f, term=term))
+    a, b = Term(), term
+
+    while a != b:
+        a, b = b, traverse_bottom_up(f=f, term=traverse_top_down(f=f, term=term))
+    
+    return b
 
 def traverse_bottom_up(f : Callable[[Term], Term], term : Term) -> Term:
     """