# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1382828525 -7200
# Node ID 354ef688b44695a4876f592cef2af9f94acf5e2d
# Parent  17378d84907359a9bdea94301fc5cfdb0e9f6ba7
Added "reverse" branches in order to immediately obtain assignment details.

diff -r 17378d849073 -r 354ef688b446 docs/annotations.txt
--- a/docs/annotations.txt	Sun Oct 27 01:00:27 2013 +0200
+++ b/docs/annotations.txt	Sun Oct 27 01:02:05 2013 +0200
@@ -67,8 +67,14 @@
                     branch
 _attrbranches       indicates the immediate contributors to attribute usage
                     known to a node
+_attrrevbranches    indicates the immediate recipients of attribute usage known
+                    to a node (and is thus the inverse of _attrbranches)
 _attrcontributors   defines nodes contributing to combined attribute usage known
-                    to a node
+                    to a node (and is thus the accumulation of all contributors
+                    via branches)
+_attrdefs           defines definition-related users which consume usage details
+                    from the node (and is thus the accumulation of all
+                    definitions affected by the node)
 _attrcombined       defines a dictionary mapping local names to sets of
                     attribute names found to be used with those names for the
                     entire lifetime of a particular attribute user
@@ -78,8 +84,6 @@
                     region of the code
 _attrspecifictypes  defines specific types from merged attribute usage details
                     (for non-user nodes)
-_attrdefs           defines definition-related users which consume usage details
-                    from the node
 
 Attribute Accessors
 -------------------
diff -r 17378d849073 -r 354ef688b446 micropython/branch.py
--- a/micropython/branch.py	Sun Oct 27 01:00:27 2013 +0200
+++ b/micropython/branch.py	Sun Oct 27 01:02:05 2013 +0200
@@ -381,6 +381,11 @@
         if node._attrbranches is None:
             node._attrbranches = []
 
+        # Branches receiving usage from this node.
+
+        if node._attrrevbranches is None:
+            node._attrrevbranches = []
+
         # Definitions receiving usage from this node.
 
         if node._attrdefs is None:
@@ -537,6 +542,7 @@
         for user in all_users:
             self._init_attribute_user(user)
             user._attrbranches.append(node)
+            node._attrrevbranches.append(user)
 
     def _abandon_branch(self, retain_branch=True):
 
diff -r 17378d849073 -r 354ef688b446 micropython/data.py
--- a/micropython/data.py	Sun Oct 27 01:00:27 2013 +0200
+++ b/micropython/data.py	Sun Oct 27 01:02:05 2013 +0200
@@ -550,21 +550,39 @@
     def __init__(self, position, parent, name, nodes):
         BaseAttr.__init__(self, position, parent, name)
         self.nodes = nodes or set()
+        self.users = None
+
+    def _get_defining_users(self):
+        if self.users is None:
+            users = set()
+            visited = set()
+            for node in self.nodes:
+                self._get_defining_users_for_node(node, visited, users)
+            self.users = users
+        return self.users
+
+    def _get_defining_users_for_node(self, node, visited, users):
+        if node in visited:
+            return
+        visited.add(node)
+        if not node._attrrevbranches:
+            if node._values and node._values.has_key(self.name):
+                users.add(node)
+            return
+        for n in node._attrrevbranches:
+            self._get_defining_users_for_node(n, visited, users)
 
     def get_assignments(self):
-        # NOTE: Needs to consider loops.
-        return len(self.nodes)
+        return len(self._get_defining_users())
 
     def get_context_values(self):
         context_values = set()
-        for node in self.nodes:
-            for def_user in node._attrdefs or [node]:
-                if def_user._values and def_user._values.has_key(self.name):
-                    attr = def_user._values[self.name]
-                    if isinstance(attr, BaseAttr):
-                        context_values.update(attr.get_context_values())
-                    else:
-                        context_values.add(get_context_and_value(attr))
+        for def_user in self._get_defining_users():
+            attr = def_user._values[self.name]
+            if isinstance(attr, BaseAttr):
+                context_values.update(attr.get_context_values())
+            else:
+                context_values.add(get_context_and_value(attr))
         return context_values
 
 class Attr(BaseAttr):