From fcd8b75ed6a5faa1cc87e1209fa4d7dfbef30628 Mon Sep 17 00:00:00 2001
From: ctsk <9384305+ctsk@users.noreply.github.com>
Date: Fri, 9 Sep 2022 12:35:27 +0200
Subject: [PATCH] Expression pretty printer

---
 .../main/java/xyz/ctsk/lox/AstPrinter.java    | 39 +++++++++++++++++++
 .../main/java/xyz/ctsk/lox/Interpreter.java   |  2 +-
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/jlox/lox/src/main/java/xyz/ctsk/lox/AstPrinter.java b/jlox/lox/src/main/java/xyz/ctsk/lox/AstPrinter.java
index fa0be09..60ae97c 100644
--- a/jlox/lox/src/main/java/xyz/ctsk/lox/AstPrinter.java
+++ b/jlox/lox/src/main/java/xyz/ctsk/lox/AstPrinter.java
@@ -9,6 +9,10 @@ public class AstPrinter {
         return expr.accept(new Polish(parentheses, true));
     }
 
+    public static String pretty(Expr expr) {
+        return expr.accept(new Pretty());
+    }
+
     private record Polish(boolean parentheses, boolean reverse) implements Expr.Visitor<String> {
         @Override
         public String visitAssignExpr(Expr.Assign expr) {
@@ -62,4 +66,39 @@ public class AstPrinter {
             }
         }
     }
+
+    private static class Pretty implements Expr.Visitor<String> {
+        @Override
+        public String visitAssignExpr(Expr.Assign expr) {
+            return String.join(" ", expr.name().lexeme(), "=", expr.value().accept(this));
+        }
+
+        @Override
+        public String visitBinaryExpr(Expr.Binary expr) {
+            return String.join(" ",
+                    expr.left().accept(this),
+                    expr.operator().lexeme(),
+                    expr.right().accept(this));
+        }
+
+        @Override
+        public String visitGroupingExpr(Expr.Grouping expr) {
+            return '(' + expr.expression().accept(this) + ')';
+        }
+
+        @Override
+        public String visitLiteralExpr(Expr.Literal expr) {
+            return Interpreter.stringify(expr.value());
+        }
+
+        @Override
+        public String visitUnaryExpr(Expr.Unary expr) {
+            return expr.operator().lexeme() + expr.right().accept(this);
+        }
+
+        @Override
+        public String visitVariableExpr(Expr.Variable expr) {
+            return expr.name().lexeme();
+        }
+    }
 }
diff --git a/jlox/lox/src/main/java/xyz/ctsk/lox/Interpreter.java b/jlox/lox/src/main/java/xyz/ctsk/lox/Interpreter.java
index e9f0bfe..a40c565 100644
--- a/jlox/lox/src/main/java/xyz/ctsk/lox/Interpreter.java
+++ b/jlox/lox/src/main/java/xyz/ctsk/lox/Interpreter.java
@@ -32,7 +32,7 @@ public class Interpreter implements Expr.Visitor<Object>, Stmt.Visitor<Void> {
         return expr.accept(this);
     }
 
-    private String stringify(Object object) {
+    static String stringify(Object object) {
         if (object == null) return "nil";
 
         var text = object.toString();