1 files changed, 16 insertions, 5 deletions
diff --git a/impl/Operator.hpp b/impl/Operator.hpp
index 2c5af75..c9b4a06 100644
--- a/impl/Operator.hpp
+++ b/impl/Operator.hpp
@@ -3,7 +3,6 @@
 
 template<typename T>
 T infinity() { }
-
 template<>
 float infinity() {
   return INFINITY;
@@ -60,12 +59,24 @@ struct Constant : public Operator<T> {
 
 template<typename T>
 struct Addition: public Operator<T> {
-  Addition(int i) : _value(i) { }
   T operator() (const std::vector< Expression<T>* >& args, const VariableAssignment<T>& ass) const {
-    return (*args[0])(ass) + _value;
+    T sum = (*args[0])(ass);
+    for (unsigned int i = 1, size = args.size(); i < size; ++i) {
+      sum += (*args[i])(ass);
+    }
+    return sum;
+  }
+};
+
+template<typename T>
+struct Subtraction: public Operator<T> {
+  T operator() (const std::vector< Expression<T>* >& args, const VariableAssignment<T>& ass) const {
+    T sum = (*args[0])(ass);
+    for (unsigned int i = 1, size = args.size(); i < size; ++i) {
+      sum -= (*args[i])(ass);
+    }
+    return sum;
   }
-  private:
-  int _value;
 };
 
 #include "VariableAssignment.hpp"