diff -r 0bcc13460dae -r 65efd0c6919f pgtoolkit/pgdiff.py
--- a/pgtoolkit/pgdiff.py	Thu Jan 24 17:11:17 2013 +0100
+++ b/pgtoolkit/pgdiff.py	Fri Jan 25 17:06:54 2013 +0100
@@ -118,6 +118,18 @@
         self.name = table
 
 
+class DiffArgument(DiffBase):
+    def __init__(self, change, schema, function, argument):
+        DiffBase.__init__(self)
+        self.level = 2
+        self.type = 'argument'
+        self.change = change
+        self.schema = schema
+        self.function = function
+        self.argument = argument
+        self.name = argument
+
+
 class DiffFunction(DiffBase):
     def __init__(self, change, schema, function):
         DiffBase.__init__(self)
@@ -247,16 +259,6 @@
             if x not in src:
                 yield ('+', x)
 
-    def _compare_functions(self, a, b):
-        diff = []
-        if a.arguments != b.arguments:
-            diff.append(('args', a.arguments, b.arguments))
-        if a.result != b.result:
-            diff.append(('result', a.result, b.result))
-        if a.source != b.source:
-            diff.append(('source', a.source, b.source))
-        return diff
-
     def _compare_columns(self, a, b):
         diff = []
         if a.type != b.type:
@@ -275,6 +277,24 @@
             diff.append(('definition', a.definition, b.definition))
         return diff
 
+    def _compare_functions(self, a, b):
+        diff = []
+        if a.result != b.result:
+            diff.append(('result', a.result, b.result))
+        if a.source != b.source:
+            diff.append(('source', a.source, b.source))
+        return diff
+
+    def _compare_arguments(self, a, b):
+        diff = []
+        if a.type != b.type:
+            diff.append(('type', a.type, b.type))
+        if a.mode != b.mode:
+            diff.append(('mode', a.mode, b.mode))
+        if a.default != b.default:
+            diff.append(('default', a.default, b.default))
+        return diff
+
     def _diff_columns(self, schema, table, src_columns, dst_columns):
         for nd in self._diff_names(src_columns, dst_columns):
             if nd[1] in dst_columns:
@@ -336,16 +356,37 @@
             else:
                 yield tdo
 
+    def _diff_arguments(self, schema, function, src_args, dst_args):
+        for nd in self._diff_names(src_args, dst_args):
+            ado = DiffArgument(change=nd[0], schema=schema, function=function, argument=nd[1])
+            if nd[0] == '*':
+                a = src_args[nd[1]]
+                b = dst_args[nd[1]]
+                ado.changes = self._compare_arguments(a, b)
+                if ado.changes:
+                    yield ado
+            else:
+                yield ado
+
     def _diff_functions(self, schema, src_functions, dst_functions):
         for nd in self._diff_names(src_functions, dst_functions):
             fdo = DiffFunction(change=nd[0], schema=schema, function=nd[1])
             if nd[0] == '*':
-                # compare function body and arguments
+                # compare function body and result
                 a = src_functions[nd[1]]
                 b = dst_functions[nd[1]]
                 fdo.changes = self._compare_functions(a, b)
                 if fdo.changes:
                     yield fdo
+                    fdo = None
+                # arguments
+                src_args = src_functions[nd[1]].arguments
+                dst_args = dst_functions[nd[1]].arguments
+                for ado in self._diff_arguments(schema, nd[1], src_args, dst_args):
+                    if fdo:
+                        yield fdo
+                        fdo = None
+                    yield ado
             else:
                 yield fdo