From 6a27431f816e264abf90d4fdc2b4dcec480caccd Mon Sep 17 00:00:00 2001
From: David Beazley <dave@dabeaz.com>
Date: Sat, 8 Sep 2018 15:26:00 -0500
Subject: [PATCH] Fixed Issue #14.

---
 CHANGES     | 3 +++
 sly/yacc.py | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/CHANGES b/CHANGES
index 85ab6c7..18e4d93 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,5 +1,8 @@
 Version 0.4
 -----------
+9/8/2018   Fixed Issue #14.  YaccProduction index property causes
+           AttributeError if index is 0
+
 9/5/2018   Added support for getattr() and related functions on
            productions.
 
diff --git a/sly/yacc.py b/sly/yacc.py
index b6a6710..5e2fa9d 100644
--- a/sly/yacc.py
+++ b/sly/yacc.py
@@ -139,7 +139,7 @@ class YaccProduction:
             if isinstance(tok, YaccSymbol):
                 continue
             index = getattr(tok, 'index', None)
-            if index:
+            if index is not None:
                 return index
         raise AttributeError('No index attribute found')