1 files changed, 25 insertions, 2 deletions
diff --git a/src/com/craftinginterpreters/lox/Interpreter.java b/src/com/craftinginterpreters/lox/Interpreter.java
index 3e3be86..4092191 100644
--- a/src/com/craftinginterpreters/lox/Interpreter.java
+++ b/src/com/craftinginterpreters/lox/Interpreter.java
@@ -1,11 +1,14 @@
 package com.craftinginterpreters.lox;
 
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 class Interpreter implements Expr.Visitor<Object>, Stmt.Visitor<Void> {
     final Environment globals = new Environment();
     private Environment environment = globals;
+    private final Map<Expr, Integer> locals = new HashMap<>();
 
     Interpreter() {
         globals.define("clock", new LoxCallable() {
@@ -64,7 +67,16 @@ class Interpreter implements Expr.Visitor<Object>, Stmt.Visitor<Void> {
 
     @Override
     public Object visitVariableExpr(Expr.Variable expr) {
-        return environment.get(expr.name);
+        return lookUpVariable(expr.name, expr);
+    }
+
+    private Object lookUpVariable(Token name, Expr expr) {
+        Integer distance = locals.get(expr);
+        if (distance != null) {
+            return environment.getAt(distance, name.lexeme);
+        } else {
+            return globals.get(name);
+        }
     }
 
     private void checkNumberOperand(Token operator, Object operand) {
@@ -125,6 +137,10 @@ class Interpreter implements Expr.Visitor<Object>, Stmt.Visitor<Void> {
         stmt.accept(this);
     }
 
+    public void resolve(Expr expr, int depth) {
+        locals.put(expr, depth);
+    }
+
     public void executeBlock(List<Stmt> statements, Environment environment) {
         Environment previous = this.environment;
 
@@ -208,7 +224,14 @@ class Interpreter implements Expr.Visitor<Object>, Stmt.Visitor<Void> {
     @Override
     public Object visitAssignExpr(Expr.Assign expr) {
         Object value = evaluate(expr.value);
-        environment.assign(expr.name, value);
+
+        Integer distance = locals.get(expr);
+        if (distance != null) {
+            environment.assignAt(distance, expr.name, value);
+        } else {
+            globals.assign(expr.name, value);
+        }
+
         return value;
     }