Merge branch 'hash' into 'master'

Specialize std::hash<T> for Cell, Vector2, Vector3

See merge request walberla/walberla!221

src/core/cell/Cell.h

@@ -381,3 +381,15 @@ namespace mpi
 
 
 } // namespace walberla
+
+namespace std
+{
+   template<>
+   struct hash< walberla::Cell >
+   {
+      std::size_t operator()( walberla::Cell const & cell ) const noexcept
+      {
+         return walberla::cell::hash_value( cell );
+      }
+   };
+} // namespace std

src/core/math/Vector2.h

@@ -1689,3 +1689,15 @@ namespace walberla {
    };
 
 } // namespace walberla
+
+namespace std
+{
+    template<typename T>
+    struct hash< walberla::Vector2<T> >
+    {
+        std::size_t operator()( walberla::Vector2<T> const & v ) const noexcept
+        {
+            return walberla::Vector2<T>::hash_value( v );
+        }
+    };
+} // namespace std

src/core/math/Vector3.h

@@ -1969,3 +1969,15 @@ inline bool check_float_equal_eps( const math::Vector3<real_t> & lhs, const math
 }
 }
 }
+
+namespace std
+{
+    template<typename T>
+    struct hash< walberla::Vector3<T> >
+    {
+        std::size_t operator()( walberla::Vector3<T> const & v ) const noexcept
+        {
+            return walberla::Vector3<T>::hash_value( v );
+        }
+    };
+} // namespace std