21aa0f33   
   From: daniel.kruegler@googlemail.com   
      
   Am 22.09.2011 21:46, schrieb clonet:   
   > To make an example:   
   > I have an IOBase class and some specialized classes derived from   
   > IOBase (e.g.: IOBuffered, IOSingle, ...).   
   > Now I need to define a template class which should work on all types   
   > of IO.   
   >   
   > Something like:   
   >   
   > template   
      
   Don't use such a parameter name, if you are not a standard library   
   implementor! Names with an underscore followed by an uppercase latter are   
   reserved to an implementation for *any* use ([global.names] p1).   
      
   > class {   
   >  ....   
   > }   
   >   
   > Now, the problem is: is there a way to force the library user to   
   > specify a class derived from IOBase as _TIO?   
   >   
   > In java generics one can use constructs like ...... ,   
   > in C++?   
      
   The most relevant question would be: What should happen, if the   
   type does not satisfy the constraints? If a reasonable error message is   
   sufficient, you could write:   
      
   #include    
      
   template    
   class X {   
   static_assert(std::is_base_of::value, "Template argument must be   
   equal to IOBase or derived from IOBase");   
   ....   
   };   
      
   for a strict derivation requirement you can express this as   
      
   std::is_base_of::value && !std::is_same::value   
      
   HTH & Greetings from Bremen,   
      
   Daniel Krügler   
      
      
      
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