Changes between Version 2 and Version 3 of Scopes

Timestamp:

04/20/11 08:28:30 (15 years ago)

Author:

Stephen Siegel

Comment:

--

Scopes

@@ -4 +4 @@
 This will require changes to front, model, dynamic, state layers.
 
-== Changed to model layer ==
+Scopes form a tree.
+
+== model layer ==
+
+A local variable will now have associated to it an instance of ScopeIF:
 
 ScopeIF:
@@ -15 +19 @@
  * ScopeIF newScope(ScopeIF parentScope);
  * LocationIF newLocation(ScopeIF scope, ...);
- * methods to create locations need to specify scope instead of function
+ * all methods to create locations need to specify scope instead of function
 
 FunctionIF:
- * /* creating a function creates one scope automatically: */
+ * creating a function creates one scope automatically: the outer-most local scope
  * ScopeIF outerScope(); 
+
+
+== front layer ==
+
+In generating model, you need to keep track of which scope you are in.
+Use a stack.
+When you enter a block, push.  When you exit a block pop.
+
+== state layer ==
+
+The state of a Frame on the call stack now changes.
+In place of list of local variables, there is stack of scopes: each entry gives the state of that scope.
+The state of the scope gives the list of variable values in that scope.
+
+== transitions ==
+
+when moving from location to another, look at scope.  If it changes, you need to pop up the tree, and push down the tree,
+to get to the new scope.   When you push, you need to initialize the new local variables correctly.
+
+Find out in C what happens when you jump into the middle of a block: how are variables initialized?