Started with a very first attempt for the OR operator

Update #127

src/dataspace/selection.cpp

@@ -235,6 +235,20 @@ void Hyperslab::apply(const Dataspace &space,SelectionOperation ops) const
   }
 }
 
+SelectionList operator|(const Hyperslab &a,const Hyperslab &b)
+{
+  return {{SelectionOperation::SET,Selection::SharedPointer(new Hyperslab(a))},
+    {SelectionOperation::OR,Selection::SharedPointer(new Hyperslab(b))}
+  };
+}
+
+SelectionList &operator|(SelectionList &selections,const Hyperslab &b)
+{
+  selections.push_back({SelectionOperation::SET,
+    Selection::SharedPointer(new Hyperslab(b))});
+  return selections;
+}
+
 
 Points::Points():
     Selection()

src/include/h5cpp/dataspace/selection.hpp

@@ -28,6 +28,8 @@
 #include <h5cpp/dataspace/dataspace.hpp>
 #include <h5cpp/types.hpp>
 #include <h5cpp/windows.hpp>
+#include <memory>
+#include <list>
 
 namespace hdf5 {
 namespace dataspace {
@@ -38,6 +40,13 @@ namespace dataspace {
 class DLL_EXPORT Selection
 {
   public:
+    //!
+    //! \brief pointer for selection stacks
+    //!
+    //! As selections use virtual functions for being applied we have to
+    using UniquePointer = std::unique_ptr<Selection>;
+    using SharedPointer = std::shared_ptr<Selection>;
+
     //!
     //! \brief default constructor
     //!
@@ -73,6 +82,9 @@ class DLL_EXPORT Selection
                        SelectionOperation ops) const = 0;
 };
 
+using SelectionPair = std::pair<SelectionOperation,Selection::SharedPointer>;
+using SelectionList = std::list<SelectionPair>;
+
 //!
 //! \brief hyperslab selection class
 //!
@@ -308,6 +320,9 @@ class DLL_EXPORT Hyperslab : public Selection
 
 };
 
+SelectionList operator|(const Hyperslab &a,const Hyperslab &b);
+SelectionList& operator|(SelectionList &selections,const Hyperslab &b);
+
 
 class DLL_EXPORT Points : public Selection
 {