Question

I have a templated function fct that uses some complex data structure based on the template parameter. It also calls some helper functions (templated on the same type) that are in a separate helpers namespace and use the same complex data structure. Now it gets really ugly because we cannot make one typedef for the complex type that all functions can access:

namespace helpers {   template<class T>   void h1(const std::vector< std::vector< std::map<T, std::set<T> > > >& bar){     // ...   } }  template<class T> void fct(const std::vector< std::vector< std::map<T, std::set<T> > > >& bar){   // ...   helpers::h1(bar); } 

Now I want to make it prettier, by using one typedef that all functions can use.

A templated typedef would be nice, but it’s not allowed:

template<class T>  typedef std::vector< std::vector< std::map<T, std::set<T> > > > Bar; 

Another solution would be, I think, to wrap all these functions in a templated namespace, but that’s not allowed in C++ either (I heard it will be in `C++0x’ …).

We have of course templated classes, but note that I don’t really want the user to have to construct an object and call member functions on it. So the workaround I ended up using was to use a templated class where all member functions are static:

template<class T> class All {    typedef std::vector< std::vector< std::map<T, std::set<T> > > > Bar;    static void fct(const Bar& bar){     // ...     h1(bar);   }  private:   static void h1(const Bar& bar){     // ...   } }; 

My question is: It’s probably a bit funny if large parts of my code are organized like that? After all it’s a bit unusual to have many classes with just static member functions? Are there other solutions/workaround that make the ‘templated typedef’ / ‘templated namespace’ possible?

Answer 1

Are there other solutions/workaround that make the ‘templated typedef’ / ‘templated namespace’ possible?

GOTW #79: Template Typedef

The New C++ Typedef Templates (See Section 1: The Problem and Current Workarounds)