From f2ddb3349fa32bdcf77e0ba721920cfc3971b22d Mon Sep 17 00:00:00 2001
From: Arash Partow <partow@gmail.com>
Date: Tue, 17 Apr 2018 10:13:24 +1000
Subject: [PATCH] C++ Mathematical Expression Library (ExprTk) 
 http://www.partow.net/programming/exprtk/index.html

---
 exprtk.hpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/exprtk.hpp b/exprtk.hpp
index 670eda9..ab34a4f 100644
--- a/exprtk.hpp
+++ b/exprtk.hpp
@@ -17722,6 +17722,13 @@ namespace exprtk
          control_block_->ref_count++;
       }
 
+      expression(const symbol_table<T>& symbol_table)
+      : control_block_(0)
+      {
+         set_expression(new details::null_node<T>());
+         symbol_table_list_.push_back(symbol_table);
+      }
+
       inline expression<T>& operator=(const expression<T>& e)
       {
          if (this != &e)