diff --git a/include/nana/filesystem/filesystem.hpp b/include/nana/filesystem/filesystem.hpp
index a3a3e373..61ce8223 100644
--- a/include/nana/filesystem/filesystem.hpp
+++ b/include/nana/filesystem/filesystem.hpp
@@ -40,18 +40,14 @@
 
 #include <nana/deploy.hpp>
 
- // namespace std { namespace experimental { namespace filesystem { inline namespace v1 {
-
-namespace nana  { namespace experimental { 	
-
-#ifndef CXX_NO_INLINE_NAMESPACE
-inline namespace v1
+namespace nana  { namespace experimental { namespace filesystem
 {
+#ifndef CXX_NO_INLINE_NAMESPACE
+			inline namespace v1
+			{
 #endif
 
-namespace filesystem
-{
-	enum class file_type 
+				enum class file_type
 	{ 
 		none = 0,   ///< has not been determined or an error occurred while trying to determine
 		not_found = -1, ///< Pseudo-type: file was not found. Is not considered an error
diff --git a/include/nana/filesystem/filesystem_ext.hpp b/include/nana/filesystem/filesystem_ext.hpp
index 1f5d4317..0e75b249 100644
--- a/include/nana/filesystem/filesystem_ext.hpp
+++ b/include/nana/filesystem/filesystem_ext.hpp
@@ -15,6 +15,7 @@
 #ifndef NANA_FILESYSTEM_EXT_HPP
 #define NANA_FILESYSTEM_EXT_HPP
 
+namespace nana {namespace experimental {namespace filesystem {namespace ext {
 #if defined(NANA_WINDOWS)
     constexpr auto def_root = "C:";
     constexpr auto def_rootstr = "C:\\";
@@ -27,4 +28,17 @@
 
 // nana::experimental::filesystem::path_user());   //  REPLACE !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! to filesystem_ext.hhp
 
+template<class DI> // DI = directory_iterator from std, boost, or nana
+class directory_only_iterator : public DI
+{
+   // if (!this->is_directory()) continue;
+};
+
+template<class DI> // DI = directory_iterator from std, boost, or nana
+class regular_file_only_iterator : public DI
+{
+    // if (this->is_directory()) continue;
+};
+
+    }}}}
 #endif //NANA_FILESYSTEM_EXT_HPP
diff --git a/include/nana/filesystem/filesystem_selector.hpp b/include/nana/filesystem/filesystem_selector.hpp
index a91e903d..b168ce30 100644
--- a/include/nana/filesystem/filesystem_selector.hpp
+++ b/include/nana/filesystem/filesystem_selector.hpp
@@ -31,29 +31,40 @@
 #if defined(NANA_BOOST_FILESYSTEM_AVAILABLE) && ( defined(NANA_BOOST_FILESYSTEM_FORCE) || (defined(STD_FILESYSTEM_NOT_SUPPORTED) && defined(NANA_BOOST_FILESYSTEM_PREFERRED) ) )
 
 #   include <boost/filesystem.hpp>
+
 	// add boost::filesystem into std::experimental::filesystem
-	namespace std {
-		namespace experimental {
+namespace std {
+	namespace experimental {
+		namespace filesystem {
+
 #       ifdef CXX_NO_INLINE_NAMESPACE
-			using namespace boost::experimental;
+				using namespace boost::experimental::filesystem;
 #       else
-			using namespace boost::experimental::v3;
+				using namespace boost::experimental::filesystem::v3;
 #       endif
 
-		}
+		} // filesystem
+	} // experimental
+} // std
+
 
 #elif defined(STD_FILESYSTEM_NOT_SUPPORTED)
 
 #   include <nana/filesystem/filesystem.hpp>
-	namespace std {
-		namespace experimental {
+
+namespace std {
+	namespace experimental {
+		namespace filesystem {
+
 #       ifdef CXX_NO_INLINE_NAMESPACE
-			using namespace nana::experimental;
+				using namespace nana::experimental::filesystem;
 #       else
-			using namespace nana::experimental::v1;
+				using namespace nana::experimental::filesystem::v1;
 #       endif
-		}
-}
+
+		} // filesystem
+	} // experimental
+} // std
 
 #else
 #    include <filesystem>
diff --git a/source/filesystem/filesystem.cpp b/source/filesystem/filesystem.cpp
index aca26162..3f432fbd 100644
--- a/source/filesystem/filesystem.cpp
+++ b/source/filesystem/filesystem.cpp
@@ -37,12 +37,12 @@
 #endif
 
 
-namespace nana {	namespace experimental {
-#ifndef CXX_NO_INLINE_NAMESPACE
-	inline namespace v1 {
-#endif
-	namespace filesystem
+namespace nana {	namespace experimental {	namespace filesystem
 	{
+#ifndef CXX_NO_INLINE_NAMESPACE
+			inline namespace v1 {
+#endif
+
 		//class filesystem_error
 			filesystem_error::filesystem_error(const std::string& msg, std::error_code err)
 				: std::system_error(err, msg)