@@ 5,24 5,32 @@ def proximity(klass, mro):
 
 def lexicographic_mro(signature, matches):
     "dispatch ranking similar to CLOS"
-    mros = tuple(klass.mro() for klass in signature)
+    mros = tuple(klass.__mro__ for klass in signature)
     return sorted((map(proximity, sig, mros), func)
                   for sig, func in matches)
 
+def clos_mro(types_func_map, callsig):
+    siglen = len(callsig)
+    table = ((sig, func) for sig, func in types_func_map.iteritems()
+             if len(sig) == siglen
+             and reduce(mul, map(issubclass, callsig, sig)))
+    return (x[1] for x in lexicographic_mro(callsig, table))
+
 class GF(object):
-    def __init__(self):
-        self._table = []
+    def __init__(self, mro=clos_mro):
+        self.mro = mro
+        self._reg = {}
         self._cache = {}
 
     def register(self, sig, func):
-        self._table.append((tuple(sig), func))
+        self._reg[tuple(sig)] = func
         self._cache = {}
 
-    def __call__(self, *args):
+    def __call__(self, *args, **kwargs):
         sig = tuple(x.__class__ for x in args)
         func = self._cache.get(sig)
         if func is None:
-            self._funcs = self.compute_mro(sig)
+            self._funcs = self.mro(self._reg, sig)
             try:
                 self._cache[sig] = func = self._funcs.next()
             except StopIteration:

          
@@ 33,10 41,4 @@ class GF(object):
         func = self._funcs.next()
         return func(*args)
 
-    def compute_mro(self, callsig):
-        siglen = len(callsig)
-        table = ((sig, func) for sig, func in self._table
-                 if len(sig) == siglen
-                 and reduce(mul, map(issubclass, callsig, sig)))
-        return (x[1] for x in lexicographic_mro(callsig, table))