Made a pass on the document

sources/core/plugins_manager.h

@@ -47,6 +47,13 @@ class plugins_manager
 		static
 #endif
 		function* get_function(const arguments& args) ;
+		
+		//! \brief get an instance of the function that is defined in the plugin with
+		//! filename n. Return null if no one exist.
+#ifdef USING_STATIC
+		static
+#endif
+		ptr<function> get_function(const arguments& args) ;
 
 		//! \brief load a function from the ALTA input file.
 #ifdef USING_STATIC

sources/core/ptr.h

@@ -47,18 +47,30 @@ template<class T> class ptr
 			_counter->decrement();
 			if(_counter->value() == 0)
 			{
-				delete _ptr;
+				if(_ptr != NULL) { delete _ptr; }
 				delete _counter;
 			}
 		}
 
 		//! Evaluation operator. This operator should be inlined for 
 		//! performance reasons.
-		inline T* operator-> ()
+		inline T* operator-> () const
 		{
 			return _ptr;
 		}
 
+		//! Raw acces to the pointer. It is sometimes needed to 
+		inline T* get() const
+		{
+			return _ptr;
+		}
+
+		//! Is the underlying pointer NULL.
+		inline bool is_null() const
+		{
+			return _ptr == NULL;
+		}
+
 	private:
 		T* _ptr;
 		ptr_counter* _counter;