From 24659dee922dd41ad0b978642e76b26d2fdb2e15 Mon Sep 17 00:00:00 2001
From: deepak gupta <deepak.dce01@gmail.com>
Date: Sun, 2 Sep 2012 14:26:39 +0200
Subject: [PATCH] Fixed #4087

---
 lib/mathlib.cpp      | 3 +++
 test/testmathlib.cpp | 1 +
 2 files changed, 4 insertions(+)

diff --git a/lib/mathlib.cpp b/lib/mathlib.cpp
index 799e61ae8..2c67426ff 100644
--- a/lib/mathlib.cpp
+++ b/lib/mathlib.cpp
@@ -217,6 +217,9 @@ std::string MathLib::subtract(const std::string &first, const std::string &secon
         return toString<bigint>(toLongNumber(first) - toLongNumber(second));
     }
 
+    if (first == second)
+        return "0.0" ;
+
     double d1 = toDoubleNumber(first);
     double d2 = toDoubleNumber(second);
 
diff --git a/test/testmathlib.cpp b/test/testmathlib.cpp
index 62e43c94c..2837fb7cc 100644
--- a/test/testmathlib.cpp
+++ b/test/testmathlib.cpp
@@ -123,6 +123,7 @@ private:
         ASSERT_EQUALS("5"   , MathLib::divide("25.5", "5.1"));
         ASSERT_EQUALS("7"   , MathLib::divide("21.", "3"));
         ASSERT_EQUALS("1"   , MathLib::divide("3", "2"));
+        ASSERT_EQUALS("0.0" , MathLib::subtract("0.0", "0.0"));
 
         // Unknown action should throw exception
         ASSERT_THROW(MathLib::calculate("1","2",'j'),InternalError);