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