From 96f3f986da5a950997f09797b740605591735e3b Mon Sep 17 00:00:00 2001
From: Arash Partow <partow@gmail.com>
Date: Tue, 10 Apr 2012 23:31:58 +1000
Subject: [PATCH] C++ Mathematical Expression Library (ExprTk) 
 http://www.partow.net/programming/exprtk/index.html

---
 exprtk.hpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/exprtk.hpp b/exprtk.hpp
index 0a2e541..851d622 100644
--- a/exprtk.hpp
+++ b/exprtk.hpp
@@ -3665,7 +3665,7 @@ namespace exprtk
       {
          static std::string null_stringvar;
          if (!valid_symbol(symbol_name))
-            return null_var;
+            return null_stringvar;
          else if (1 == symbol_name.size())
          {
             stringvar_pair_t& svp = short_stringvar_lut_[static_cast<std::size_t>(symbol_name[0])];
@@ -3678,7 +3678,7 @@ namespace exprtk
          {
             svm_const_itr_t itr = stringvar_map_.find(symbol_name);
             if (stringvar_map_.end() == itr)
-               return null_var;
+               return null_stringvar;
             else
                return itr->second.second->ref();
          }