Extensible environments. More powerful than necessary, but will be necessary if…

Extensible environments. More powerful than necessary, but will be necessary if scoped variables and mixins are added to the language.

context.hpp

 namespace Sass {
   using std::map;
   
+  struct Environment {
+    map<Token, Node> frame;
+    Environment* parent;
+    
+    Environment() : frame(map<Token, Node>()), parent(0)
+    { }
+    Environment(Environment* env) : frame(map<Token, Node>()), parent(env)
+    { }
+    
+    bool query(const Token& key) const
+    {
+      if (frame.count(key)) return true;
+      else if (parent)      return parent->query(key);
+      else                  return false;
+    }
+    
+    Node& operator[](const Token& key)
+    {
+      if (frame.count(key)) return frame[key];
+      else if (parent)      return (*parent)[key];
+      else                  return frame[key];
+    }
+  };
+
   struct Context {
     map<Token, Node> environment;
-    // Environment environment;
-    // map<Token, Node> mixins;
+    Environment global_env;
     vector<Node> pending;
     vector<char*> source_refs;
     size_t ref_count;
@@ -25,20 +48,4 @@ namespace Sass {
     }
   };
 
-  struct Environment {
-    vector< map<Token, Node> > stack;
-    
-    Environment()
-    : stack(vector< map<Token, Node> >())
-    {
-      stack.reserve(2);
-      stack.push_back(map<Token, Node>());
-    }
-    
-    void extend()
-    {
-      stack.push_back(map<Token, Node>());
-    }
-    
-  };
 }

node.hpp

@@ -60,15 +60,16 @@ namespace Sass {
       number,
       hex_triple,
       
-      comment,
-      
       mixin,
       parameters,
       expansion,
       arguments,
       
       variable,
-      assignment
+      assignment,
+      
+      comment,
+      none
     };
     
     static size_t fresh;
@@ -86,7 +87,7 @@ namespace Sass {
     bool from_variable;
     bool eval_me;
     
-    Node() : type(nil), children(0) { ++fresh; }
+    Node() : type(none), children(0) { ++fresh; }
   
     Node(const Node& n)
     : line_number(n.line_number),