1 files changed, 22 insertions, 0 deletions
diff --git a/impl/Sum.h b/impl/Sum.h
new file mode 100644
index 0000000..bf04669
--- /dev/null
+++ b/impl/Sum.h
@@ -0,0 +1,22 @@
+#ifndef SUM_H
+#define SUM_H
+
+#include "Expression.h"
+
+template<class T>
+struct Sum : public Expression<T> {
+  Sum(Expression<T>* left, Expression<T>* right)
+    : _left(left), _right(right) { }
+
+  T eval(const std::map<std::string, T>& mappings) const {
+    T left = _left->eval(mappings);
+    T right = _right->eval(mappings);
+    return left + right;
+  }
+  
+  private:
+  Expression<T>* _left;
+  Expression<T>* _right;
+};
+
+#endif