# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1219272555 -7200
# Node ID 5054b2ba3f9c465250d411dc0ee9b567d89f2caa
# Parent  dd607ca6396812e8ea2eb7d7db3c4eb7f3d10378
Added more support for LoadAttr and LoadAttrIndex in the RSVP implementation.

diff -r dd607ca63968 -r 5054b2ba3f9c docs/structures.txt
--- a/docs/structures.txt	Tue Aug 19 00:41:30 2008 +0200
+++ b/docs/structures.txt	Thu Aug 21 00:49:15 2008 +0200
@@ -74,12 +74,13 @@
                                             attribute; other attributes have
                                             their context preserved
 
-    LoadAttrIndex   Load attribute from     Classes, functions and modules as
-                    unknown object          the unknown object accessor cause
+    LoadAttrIndex   Load attribute from     Functions and modules as unknown
+                    object                  the unknown object accessor cause
                                             the loaded attribute to be
-                                            retrieved unchanged; whereas
+                                            retrieved unchanged; classes and
                                             instances cause the LoadAttr rules
-                                            to apply
+                                            to apply (class compatibility
+                                            applies)
 
 A certain amount of run-time testing might be required for both LoadAttr and
 LoadAttrIndex instructions. However, with certain restrictions in place around
diff -r dd607ca63968 -r 5054b2ba3f9c micropython/data.py
--- a/micropython/data.py	Tue Aug 19 00:41:30 2008 +0200
+++ b/micropython/data.py	Thu Aug 21 00:49:15 2008 +0200
@@ -271,6 +271,9 @@
         else:
             return self
 
+    def is_class_attribute(self):
+        return isinstance(self.parent, Class)
+
     def defined_within_hierarchy(self):
 
         """
diff -r dd607ca63968 -r 5054b2ba3f9c micropython/table.py
--- a/micropython/table.py	Tue Aug 19 00:41:30 2008 +0200
+++ b/micropython/table.py	Thu Aug 21 00:49:15 2008 +0200
@@ -153,9 +153,9 @@
                 else:
                     position = None # NOTE: Should fix unpositioned attributes.
 
-                # Class offset/code, context instance override flag, location/position.
+                # Class offset/code, attribute type, context instance override flag, location/position.
 
-                result.append((offset, attr.defined_within_hierarchy(), position))
+                result.append((offset, attr.is_class_attribute(), attr.defined_within_hierarchy(), position))
 
         return result
 
diff -r dd607ca63968 -r 5054b2ba3f9c rsvp.py
--- a/rsvp.py	Tue Aug 19 00:41:30 2008 +0200
+++ b/rsvp.py	Thu Aug 21 00:49:15 2008 +0200
@@ -241,12 +241,8 @@
 
     def LoadAttr(self):
         context, ref = self.value
-        loaded_context, loaded_ref = self.load(ref + self.operand)
-        if loaded_context is None:
-            # Override null context with owning instance.
-            self.value = ref, loaded_ref
-        else:
-            self.value = loaded_context, loaded_ref
+        # Retrieved context should already be appropriate for the instance.
+        self.value = self.load(ref + self.operand)
 
     def StoreAttr(self):
         context, ref = self.value
@@ -256,18 +252,24 @@
         context, ref = self.value
         code = self.load(ref) # + 0 (the classcode)
         element = self.objtable[code + self.operand]
-        found_code, found_attr = element
+        found_code, class_attr, replace_context, offset = element
         if found_code == code:
-            # NOTE: The found context should be tested against the object's context.
-            # NOTE: Compatibility between contexts should be stored in the table, or
-            # NOTE: an incompatible context should be preserved.
-            self.value = ref, found_ref
+            if class_attr:
+                loaded_context, loaded_ref = self.load(offset) # offset is address of class attribute
+                if replace_context:
+                    self.value = ref, loaded_ref # classes can also replace the context if compatible
+                    return
+                self.value = loaded_context, loaded_ref
+            else:
+                self.value = self.load(ref + offset)
         else:
             # NOTE: This should cause an attribute error.
             self.value = None
 
     def StoreAttrIndex(self): pass
 
+    # NOTE: LoadAttrIndexContext is a possibility if a particular attribute can always be overridden.
+
     def MakeFrame(self):
         self.invocation_sp_stack.append(len(self.frame_stack))
         self.frame_stack.extend([None] * self.operand)