include/wx/meta/convertible.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        wx/meta/convertible.h
   3 // Purpose:     Test if types are convertible
   4 // Author:      Arne Steinarson
   5 // Created:     2008-01-10
   6 // RCS-ID:      $Id$
   7 // Copyright:   (c) 2008 Arne Steinarson
   8 // Licence:     wxWindows licence
   9 /////////////////////////////////////////////////////////////////////////////
  10
  11 #ifndef _WX_META_CONVERTIBLE_H_
  12 #define _WX_META_CONVERTIBLE_H_
  13
  14 //
  15 // Introduce an extra class to make this header compilable with g++3.2
  16 //
  17 template <class D, class B>
  18 struct wxConvertibleTo_SizeHelper
  19 {
  20     static char Match(B* pb);
  21     static int  Match(...);
  22 };
  23
  24 // Helper to decide if an object of type D is convertible to type B (the test
  25 // succeeds in particular when D derives from B)
  26 template <class D, class B>
  27 struct wxConvertibleTo
  28 {
  29     enum
  30     {
  31         value =
  32             sizeof(wxConvertibleTo_SizeHelper<D,B>::Match(static_cast<D*>(NULL)))
  33             ==
  34             sizeof(char)
  35     };
  36 };
  37
  38 #endif // _WX_META_CONVERTIBLE_H_
  39