diff --git a/src/astprinter.rs b/src/astprinter.rs
index bc1c9a0..4e9e824 100644
--- a/src/astprinter.rs
+++ b/src/astprinter.rs
@@ -1,37 +1,57 @@
 use crate::expr::{Binary, Expr, ExprVisitor, Grouping, Literal, Unary, VisitableExpr};
 
-pub struct ASTPrinter;
+pub struct ASTPrinter {
+    pub(crate) depth: u32
+}
+
+impl ASTPrinter {
+    fn ast_tab(&self) -> String {
+        (0..self.depth).map(|_| " ").collect::<String>()
+    }
+}
 
 impl ExprVisitor for ASTPrinter {
-    fn visit_binary(&self, b: &Binary) {
-        print!("( {}", b.operator.literal);
+    fn visit_binary(&mut self, b: &Binary) {
+        println!("{}BINARY",self.ast_tab());
+        println!("{}op='{}'", self.ast_tab(), b.operator.lexeme);
+        println!("{}left=(", self.ast_tab());
+        self.depth+=1;
         b.left.accept(self);
+        self.depth-=1;
+        println!("{})", self.ast_tab());
+        println!("{}right=(", self.ast_tab());
+        self.depth+=1;
         b.right.accept(self);
-        print!(")");
+        self.depth-=1;
+        println!("{})", self.ast_tab());
     }
 
-    fn visit_grouping(&self, g: &Grouping) {
-        print!("( group ");
+    fn visit_grouping(&mut self, g: &Grouping) {
+        println!("{}GROUPING(", self.ast_tab());
+        self.depth+=1;
         g.expression.accept(self);
-        print!(")");
+        self.depth-=1;
+        print!(") ");
     }
 
-    fn visit_literal(&self, l: &Literal) {
+    fn visit_literal(&mut self, l: &Literal) {
         match l {
-            Literal::LiteralNumber(i) => print!("{}", i),
-            Literal::LiteralString(s) => print!("{}", s),
-            Literal::LiteralBool(b) => print!("{}", b),
-            Literal::LiteralNil => print!("nil"),
+            Literal::LiteralNumber(i) => print!("{}NUMBER={}", self.ast_tab(), i),
+            Literal::LiteralString(s) => print!("{}STRING='{}'", self.ast_tab(), s),
+            Literal::LiteralBool(b) => print!("{}BOOL={}", self.ast_tab(), b),
+            Literal::LiteralNil => print!("{}NIL", self.ast_tab()),
         }
     }
 
-    fn visit_unary(&self, u: &Unary) {
-        print!("( {}", u.operator.literal);
+    fn visit_unary(&mut self, u: &Unary) {
+        println!("{}UNARY(op='{}'", self.ast_tab(), u.operator.lexeme);
+        self.depth+=1;
         u.right.accept(self);
-        print!(")");
+        self.depth-=1;
+        print!(") ");
     }
 
-    fn visit_expr(&self, e: &Expr) {
+    fn visit_expr(&mut self, e: &Expr) {
         match e {
             Expr::BinaryExpr(b) => { b.accept(self); }
             Expr::GroupingExpr(g) => { g.accept(self); }
diff --git a/src/expr.rs b/src/expr.rs
index 6da9c08..8827404 100644
--- a/src/expr.rs
+++ b/src/expr.rs
@@ -30,43 +30,43 @@ pub enum Expr {
 }
 
 pub trait ExprVisitor {
-    fn visit_binary(&self, b: &Binary);
-    fn visit_grouping(&self, g: &Grouping);
-    fn visit_literal(&self, l: &Literal);
-    fn visit_unary(&self, u: &Unary);
-    fn visit_expr(&self, e: &Expr);
+    fn visit_binary(&mut self, b: &Binary);
+    fn visit_grouping(&mut self, g: &Grouping);
+    fn visit_literal(&mut self, l: &Literal);
+    fn visit_unary(&mut self, u: &Unary);
+    fn visit_expr(&mut self, e: &Expr);
 }
 
 pub trait VisitableExpr {
-    fn accept(&self, visitor: &impl ExprVisitor);
+    fn accept(&self, visitor: &mut impl ExprVisitor);
 }
 
 impl VisitableExpr for Binary {
-    fn accept(&self, visitor: &impl ExprVisitor) {
+    fn accept(&self, visitor: &mut impl ExprVisitor) {
         visitor.visit_binary(self);
     }
 }
 
 impl VisitableExpr for Grouping {
-    fn accept(&self, visitor: &impl ExprVisitor) {
+    fn accept(&self, visitor: &mut impl ExprVisitor) {
         visitor.visit_grouping(self);
     }
 }
 
 impl VisitableExpr for Literal {
-    fn accept(&self, visitor: &impl ExprVisitor) {
+    fn accept(&self, visitor: &mut impl ExprVisitor) {
         visitor.visit_literal(self);
     }
 }
 
 impl VisitableExpr for Unary {
-    fn accept(&self, visitor: &impl ExprVisitor) {
+    fn accept(&self, visitor: &mut impl ExprVisitor) {
         visitor.visit_unary(self);
     }
 }
 
 impl VisitableExpr for Expr {
-    fn accept(&self, visitor: &impl ExprVisitor) {
+    fn accept(&self, visitor: &mut impl ExprVisitor) {
         visitor.visit_expr(self);
     }
 }
diff --git a/src/rlox_interpreter.rs b/src/rlox_interpreter.rs
index f4bc270..337a127 100644
--- a/src/rlox_interpreter.rs
+++ b/src/rlox_interpreter.rs
@@ -48,8 +48,9 @@ impl RLoxInterpreter {
         let mut parser = Parser::new( scanner.tokens );
         match parser.parse() {
             Some(expr) => {
-                let printer = ASTPrinter;
+                let mut printer = ASTPrinter { depth: 0 };
                 printer.visit_expr(&expr);
+                println!();
             },
             None => println!("An error occurred while parsing expression.")
         }