From feebade3572ecf6d379ebd80161e9776d895e961 Mon Sep 17 00:00:00 2001
From: yhirose <yuji.hirose.bug@gmail.com>
Date: Sun, 8 Feb 2015 23:02:10 -0500
Subject: [PATCH] Added is_undefined method.

---
 peglib.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/peglib.h b/peglib.h
index cb2e24f..8acd0e2 100644
--- a/peglib.h
+++ b/peglib.h
@@ -67,6 +67,10 @@ public:
         delete content_;
     }
 
+    bool is_undefined() const {
+        return content_ == nullptr;
+    }
+
     template <typename T>
     T& get() {
         assert(content_);