From aa71b4da36a8947a59dd67cc1be9d0f49de1a121 Mon Sep 17 00:00:00 2001
From: Pekka Laiho <pekka.i.laiho@gmail.com>
Date: Sat, 6 Jun 2020 21:02:02 +0700
Subject: [PATCH] debugging support for eval

---
 bootstrap.php   |  2 +-
 src/Evaller.php | 21 ++++++++++++++++++++-
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/bootstrap.php b/bootstrap.php
index bb92f1f..33cb8d4 100644
--- a/bootstrap.php
+++ b/bootstrap.php
@@ -5,8 +5,8 @@ function ml_get_lisp(): array
 {
     $tokenizer = new MadLisp\Tokenizer();
     $reader = new MadLisp\Reader();
-    $eval = new MadLisp\Evaller($tokenizer, $reader);
     $printer = new MadLisp\Printer();
+    $eval = new MadLisp\Evaller($tokenizer, $reader, $printer);
 
     $lisp = new MadLisp\Lisp($tokenizer, $reader, $eval, $printer);
 
diff --git a/src/Evaller.php b/src/Evaller.php
index aaf3f6f..8bd130f 100644
--- a/src/Evaller.php
+++ b/src/Evaller.php
@@ -5,17 +5,36 @@ class Evaller
 {
     protected Tokenizer $tokenizer;
     protected Reader $reader;
+    protected Printer $printer;
 
-    public function __construct(Tokenizer $tokenizer, Reader $reader)
+    private const DEBUG = true;
+
+    public function __construct(Tokenizer $tokenizer, Reader $reader, Printer $printer)
     {
         $this->tokenizer = $tokenizer;
         $this->reader = $reader;
+        $this->printer = $printer;
     }
 
     public function eval($ast, Env $env)
     {
+        if (self::DEBUG) {
+            print("eval: ");
+            $this->printer->print($ast);
+            print("\n");
+            $loops = 0;
+        }
+
         while (true) {
 
+            if (self::DEBUG) {
+                if ($loops++ > 0) {
+                    print("eval loop: ");
+                    $this->printer->print($ast);
+                    print("\n");
+                }
+            }
+
             // Not list or empty list
             if (!($ast instanceof MList)) {
                 return $this->evalAst($ast, $env);