From 11b14cf597756f645d4b43b944f5d675c1f36512 Mon Sep 17 00:00:00 2001
From: Johann Dreo <johann.dreo@thalesgroup.com>
Date: Fri, 22 Oct 2010 10:07:09 +0200
Subject: [PATCH] Arithmetic operators (note: priority to unfeasibility)

---
 eo/src/eoDualFitness.h | 43 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/eo/src/eoDualFitness.h b/eo/src/eoDualFitness.h
index d54750ba..c57d9fcc 100644
--- a/eo/src/eoDualFitness.h
+++ b/eo/src/eoDualFitness.h
@@ -143,6 +143,48 @@ public:
 
 public:
 
+    //! Add a given fitness to the current one
+    template <class F, class Cmp>
+    friend
+    eoDualFitness<F,Cmp> & operator+=( eoDualFitness<F,Cmp> & from, const eoDualFitness<F,Cmp> & that )
+    {
+        from._value += that._value;
+
+        // true only if the two are feasible, else false
+        from._is_feasible = from._is_feasible && that._is_feasible;
+
+        return from;
+    }
+
+    //! Substract a given fitness to the current one
+    template <class F, class Cmp>
+    friend
+    eoDualFitness<F,Cmp> & operator-=( eoDualFitness<F,Cmp> & from, const eoDualFitness<F,Cmp> & that )
+    {
+        from._value -= that._value;
+
+        // true only if the two are feasible, else false
+        from._is_feasible = from._is_feasible && that._is_feasible;
+
+        return from;
+    }
+
+    // Add this fitness's value to that other, and return a _new_ instance with the result.
+    template <class F, class Cmp>
+    eoDualFitness<F,Cmp> operator+(const eoDualFitness<F,Cmp> & that) 
+    {
+        eoDualFitness<F,Cmp> from( *this );
+        return from += that;
+    }
+
+    // Add this fitness's value to that other, and return a _new_ instance with the result.
+    template <class F, class Cmp>
+    eoDualFitness<F,Cmp> operator-(const eoDualFitness<F,Cmp> & that) 
+    {
+        eoDualFitness<F,Cmp> from( *this );
+        return from -= that;
+    }
+
     //! Print an eoDualFitness instance as a pair of numbers, separated by a space
     template <class F, class Cmp>
     friend
@@ -166,7 +208,6 @@ public:
         f = std::make_pair<F,bool>( value, feasible );
         return is;
     }
-
 };
 
 //! Compare dual fitnesses as if we were maximizing