1 files changed, 17 insertions, 0 deletions
diff --git a/src/com/craftinginterpreters/lox/Environment.java b/src/com/craftinginterpreters/lox/Environment.java
index 8d8a374..0a95282 100644
--- a/src/com/craftinginterpreters/lox/Environment.java
+++ b/src/com/craftinginterpreters/lox/Environment.java
@@ -4,13 +4,25 @@ import java.util.HashMap;
 import java.util.Map;
 
 class Environment {
+    private final Environment enclosing;
     private final Map<String, Object> values = new HashMap<>();
 
+    Environment() {
+        enclosing = null;
+    }
+
+    Environment(Environment enclosing) {
+        this.enclosing = enclosing;
+    }
+
     Object get(Token name) {
         if (values.containsKey(name.lexeme)) {
             return values.get(name.lexeme);
         }
 
+        if (enclosing != null)
+            return enclosing.get(name);
+
         throw new RuntimeError(name, "Undefined variable '" + name.lexeme + "'.");
     }
 
@@ -20,6 +32,11 @@ class Environment {
             return;
         }
 
+        if (enclosing != null) {
+            enclosing.assign(name, value);
+            return;
+        }
+
         throw new RuntimeError(name, "Undefined variable '" + name.lexeme + "'.");
     }