From: daniel.kruegler@googlemail.com   
      
   Am 07.03.2012 21:21, schrieb Seungbeom Kim:   
   > On 2012-03-04 15:10, Daniel Krügler wrote:   
   >>   
   >> Ensure that your primary template is a slightly worse match (even in the   
   >> absence of constraints), then add constrained overloads. Here is an   
   >> example of what I'm thinking of:   
   >>   
   >> #include   
   >> #include   
   >>   
   >> struct Animal {};   
   >> struct Dog : Animal {};   
   >> struct Fruit {};   
   >> struct Apple : Fruit {};   
   >> struct Other {};   
   >>   
   >> template   
   >> typename std::enable_if::value>::type   
   >> do_action(T ptr) { std::cout<<  "generic"<<  std::endl; }   
   >>   
   >> template   
   >> inline void action(T* ptr) { do_action(ptr); }   
   >>   
   >> template   
   >> typename std::enable_if::value>::type   
   >> do_action(T* ptr) { std::cout<<  "animals"<<  std::endl; }   
   >>   
   >> template   
   >> typename std::enable_if::value>::type   
   >> do_action(T* ptr) { std::cout<<  "fruits"<<  std::endl; }   
   >   
   > Thank you very much, that works indeed.   
   >   
   > One question I have is: is there any reason you introduced an extra level   
   > of indirection, namely do_action? That is, wouldn't this ...   
   >   
   > template   
   > typename std::enable_if::value>::type   
   > action(T ptr) { std::cout<<  "generic"<<  std::endl; }   
   >   
   > template   
   > typename std::enable_if::value>::type   
   > action(T* ptr) { std::cout<<  "animals"<<  std::endl; }   
   >   
   > template   
   > typename std::enable_if::value>::type   
   > action(T* ptr) { std::cout<<  "fruits"<<  std::endl; }   
   >   
   > ... work as well? I tried it, and it seemed to work.   
      
   Sure. The reason why I suggested the indirection was just to provide a   
   simpler view on the primary function (For someone looking at the code it   
   may be astonishing to see this construction). It would suffice to add a   
   corresponding documentation to explain this, though.   
      
   Greetings from Bremen,   
      
   Daniel Krügler   
      
      
      
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