how to do an Enum compile time iteration

Question

I'm trying to avoid switch as much as possible and I've come up with this (not) solution. do you know if there is a way to do something like:

enum MyEnum { A, B, C, D, E, F, SIZE=F};

typedef void (*GenericFunction)(int);

template<class EnumType>
struct MyEnumTraits
{
  template<EnumType code, Args... args>
  void doStuff(args);
};

template<class EnumType, int size, MyEnumTrait>
struct Switcher
{
  Switcher()
  {
     //Do compile time initialization by populating functions_
     //doing something like: (pseudo c++ code following)

      // template metaprogramming iteration of the EnumType values: 
      //from the first to the last one (size)

     for(int i; i<size;i++)
       functions_[i] = (GenericFunction) MyEnumTrait::MyFunctionType; //
  }

  GenericFunction functions_[size];
};

template<>
struct MyEnumTraits<MyEnum>
{
  template<>
  void doStuff<A>(int a)
  {
     // do something
  }
};

template<>
struct MyEnumTraits<MyEnum>
{
  void doStuff<B,int,int>(int a, int b)
  {
    // do something else
  }
};

template<>
struct MyEnumTraits<MyEnum>
{
  template<>
  void doStuff<C, std::string>(const std::string& myString)
  {
    // do something else..
  }
};

int main()
{

  Switcher<MyEnum, SIZE> switcher;
  // Next calls will not work because I need a cast.. 
  //is there any magic I can do to avoid the cast?

  // these may work
  switcher.functions_[A](3);
  switcher.functions_[B](1,2);
  switcher.functions_[C]("bla bla");

  // this is probably impossible to do... isn't it?
  MyEnum en = /* get it from cin */;
  switcher.functions_[en](1,2,3);
}

I apologise for the bad indentation, I will try to refactor the code ASAP

[EDIT] Changed the last 3 rows of the code

Why do you apologize for the indentation? Why don't you just indent your properly before you hit "submit"? — Kerrek SB, Jun 09 '16 at 16:42
I think it is possible. I once asked a question that looks like yours, and had an answer http://stackoverflow.com/questions/37415812/simulate-the-switch-comportment-in-template-specialization — Boiethios, Jun 10 '16 at 11:00
I think the problem is a bit different because I would like to use functions with a variable number of arguments. I think that if I had to use only functions with the same signature it could have been much easier.. another thing I haven't mentioned before is that this switcher should be efficient like a switch.. too much perhaps.. — user3770392, Jun 10 '16 at 11:10
I would like to avoid macros as well, too easy with them ;) I've a different idea every 5 minutes but nothing seems working.. — user3770392, Jun 10 '16 at 11:18
I've successfully implemented some code that works using virtual methods.. the problem with this approach is that I have to manually add all the elements, so I can't use compile time initialization.. I can statically initialize it but in this way it's not reusable — user3770392, Jun 10 '16 at 15:48

how to do an Enum compile time iteration

0 Answers0