util to invoke two functors chained,

here to be used for decorating a given signal (callback)

src/lib/functorutil.hpp

@@ -0,0 +1,88 @@
+/*
+  FUNCTORUTIL.hpp  -  collection of helpers for dealing with functors and signals
+ 
+  Copyright (C)         Lumiera.org
+    2008,               Hermann Vosseler <Ichthyostega@web.de>
+ 
+  This program is free software; you can redistribute it and/or
+  modify it under the terms of the GNU General Public License as
+  published by the Free Software Foundation; either version 2 of the
+  License, or (at your option) any later version.
+ 
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+ 
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ 
+*/
+
+
+#ifndef FUNCTORUTIL_H_
+#define FUNCTORUTIL_H_
+
+#include <tr1/functional>
+
+
+
+namespace util { ////////////TODO: refactor it. But probably not directly into namespace lib. Needs some more consideration though
+  
+  using std::tr1::function;
+  using std::tr1::bind;
+  using std::tr1::placeholders::_1;
+  
+  
+  /** "Combiner" which calls two functions one after another
+   *  returning the result of the second invocation.  */
+  template<typename SIG>
+  class CombineSequenced;
+  
+  template<typename ARG, typename RET>
+  struct CombineSequenced<RET(ARG)>
+    {
+      typedef function<RET(ARG)> Func;
+      
+      static RET 
+      dispatch (Func first, Func second, ARG arg)
+        {
+          first (arg);
+          return second (arg);
+        }
+    };
+  
+  
+  template< typename SIG 
+          , class COM = CombineSequenced<SIG> 
+          >
+  class Dispatch
+    : public function<SIG>
+    {
+      typedef typename COM::Func Func;
+      
+    public:
+      Dispatch (Func const& f1,
+                Func const& f2)
+        : Func (bind (&COM::dispatch, f1, f2, _1))
+        { }
+    };
+  
+  
+  /** convenience shortcut to call two functors in sequence. 
+   *  @return a Dispatch functor object which incorporates the
+   *          functors as copy and on invocation calls the first 
+   *          function and then returns the result of the second */
+  template<typename SIG>
+  Dispatch<SIG>
+  dispatchSequenced (function<SIG> const& f1,
+                     function<SIG> const& f2)
+  {
+    return Dispatch<SIG> (f1, f2);
+  }
+  
+  
+} // namespace util
+
+#endif /*UTIL_HPP_*/