Added get_parent_directory()

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403859

dlib/dir_nav/dir_nav_extensions.cpp

@@ -34,6 +34,32 @@ namespace dlib
         }
     }
 
+// ----------------------------------------------------------------------------------------
+
+    directory get_parent_directory (
+        const directory& dir
+    )
+    {
+        return dir.get_parent();
+    }
+
+// ----------------------------------------------------------------------------------------
+
+    directory get_parent_directory (
+        const file& f
+    )
+    {
+        if (f.full_name().size() == 0)
+            return directory();
+
+        std::string::size_type pos = f.full_name().find_last_of("\\/");
+        
+        if (pos == std::string::npos)
+            return directory();
+
+        return directory(f.full_name().substr(0,pos));
+    }
+
 // ----------------------------------------------------------------------------------------
 
 }

dlib/dir_nav/dir_nav_extensions.h

@@ -93,6 +93,18 @@ namespace dlib
         ) const { return true; }
     };
 
+// ----------------------------------------------------------------------------------------
+
+    directory get_parent_directory (
+        const directory& dir
+    );
+
+// ----------------------------------------------------------------------------------------
+
+    directory get_parent_directory (
+        const file& f
+    );
+
 // ----------------------------------------------------------------------------------------
 
 }

dlib/dir_nav/dir_nav_extensions_abstract.h

@@ -91,6 +91,30 @@ namespace dlib
         !*/
     };
 
+// ----------------------------------------------------------------------------------------
+
+    directory get_parent_directory (
+        const directory& dir
+    );
+    /*!
+        ensures
+            - returns the parent directory of dir.  In particular, this
+              function returns the value of dir.get_parent()
+    !*/
+
+// ----------------------------------------------------------------------------------------
+
+    directory get_parent_directory (
+        const file& f
+    );
+    /*!
+        ensures
+            - if (f.full_name() != "") then
+                - returns the directory which contains the given file
+            - else
+                - returns a default initialized directory (i.e. directory())
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
 }

dlib/dir_nav/dir_nav_kernel_abstract.h

@@ -101,7 +101,7 @@ namespace dlib
         );
         /*!
             ensures
-                - this function is idential to file(const std::string& name)
+                - this function is identical to file(const std::string& name)
         !*/
 
         file (
@@ -243,7 +243,7 @@ namespace dlib
         );
         /*!
             ensures
-                - this function is idential to directory(const std::string& name)
+                - this function is identical to directory(const std::string& name)
         !*/
 
         directory (