From 211cd7a36342047511ae2aa501383abf263643c1 Mon Sep 17 00:00:00 2001
From: Xpol Wan <xpolife@gmail.com>
Date: Tue, 14 Jun 2016 17:20:49 +0800
Subject: [PATCH] make binary arithmetic operators for column_t non-member.

---
 include/xlnt/cell/index_types.hpp | 18 +++++++++---------
 source/cell/index_types.cpp       | 25 +++++--------------------
 2 files changed, 14 insertions(+), 29 deletions(-)

diff --git a/include/xlnt/cell/index_types.hpp b/include/xlnt/cell/index_types.hpp
index 9af99b87..a2378480 100644
--- a/include/xlnt/cell/index_types.hpp
+++ b/include/xlnt/cell/index_types.hpp
@@ -231,27 +231,27 @@ public:
     /// <summary>
     /// Return the result of adding rhs to this column.
     /// </summary>
-    column_t operator+(const column_t &rhs);
+    friend column_t operator+(column_t lhs, const column_t& rhs);
 
     /// <summary>
-    /// Return the result of adding rhs to this column.
+    /// Return the result of subtracing lhs by rhs column.
     /// </summary>
-    column_t operator-(const column_t &rhs);
+    friend column_t operator-(column_t lhs, const column_t& rhs);
 
     /// <summary>
-    /// Return the result of adding rhs to this column.
+    /// Return the result of multiply lhs by rhs column.
     /// </summary>
-    column_t operator*(const column_t &rhs);
+    friend column_t operator*(column_t lhs, const column_t& rhs);
 
     /// <summary>
-    /// Return the result of adding rhs to this column.
+    /// Return the result of divide lhs by rhs column.
     /// </summary>
-    column_t operator/(const column_t &rhs);
+    friend column_t operator/(column_t lhs, const column_t& rhs);
 
     /// <summary>
-    /// Return the result of adding rhs to this column.
+    /// Return the result of mod lhs by rhs column.
     /// </summary>
-    column_t operator%(const column_t &rhs);
+    friend column_t operator%(column_t lhs, const column_t& rhs);
 
     /// <summary>
     /// Add rhs to this column and return a reference to this column.
diff --git a/source/cell/index_types.cpp b/source/cell/index_types.cpp
index c97557b6..4b789a51 100644
--- a/source/cell/index_types.cpp
+++ b/source/cell/index_types.cpp
@@ -252,30 +252,15 @@ column_t column_t::operator++(int) { column_t copy(index); ++(*this); return cop
 /// </summary>
 column_t column_t::operator--(int) { column_t copy(index); --(*this); return copy; }
 
-/// <summary>
-/// Return the result of adding rhs to this column.
-/// </summary>
-column_t column_t::operator+(const column_t &rhs) { column_t copy(*this); copy.index += rhs.index; return copy; }
+column_t operator+(column_t lhs, const column_t& rhs) { lhs += rhs; return lhs; }
 
-/// <summary>
-/// Return the result of adding rhs to this column.
-/// </summary>
-column_t column_t::operator-(const column_t &rhs) { column_t copy(*this); copy.index -= rhs.index; return copy; }
+column_t operator-(column_t lhs, const column_t& rhs) { lhs -= rhs; return lhs; }
 
-/// <summary>
-/// Return the result of adding rhs to this column.
-/// </summary>
-column_t column_t::operator*(const column_t &rhs) { column_t copy(*this); copy.index *= rhs.index; return copy; }
+column_t operator*(column_t lhs, const column_t& rhs) { lhs *= rhs; return lhs; }
 
-/// <summary>
-/// Return the result of adding rhs to this column.
-/// </summary>
-column_t column_t::operator/(const column_t &rhs) { column_t copy(*this); copy.index /= rhs.index; return copy; }
+column_t operator/(column_t lhs, const column_t& rhs) { lhs /= rhs; return lhs; }
 
-/// <summary>
-/// Return the result of adding rhs to this column.
-/// </summary>
-column_t column_t::operator%(const column_t &rhs) { column_t copy(*this); copy.index %= rhs.index; return copy; }
+column_t operator%(column_t lhs, const column_t& rhs) { lhs %= rhs; return lhs; }
 
 /// <summary>
 /// Add rhs to this column and return a reference to this column.