How to traversal recursive template class

manpreet Best Answer 2 years ago

I want to traversal multiple depth template class. in C++98 (before c++11).

pesudo code.

template<typename T>
std::string find_type(T *ptr);
template <>
std::string find_type<std::string>(int *ptr)
{
  return "string";
}
template <>
std::string find_type<std::list>(std::list *ptr)
{
  return "list";
}
template <>
std::string find_type<std::vector>(std::vector *ptr)
{
  return "vector";
}

template<T>
std::string somefunction(T *ptr)
{
 if(T is template class)
   return find_type + " " + somefunction(ptr);
else
 return find_type(ptr);
}

I want to below result :

 std::list<std::string> test;
somefunction(test) -> I NEED "list string";

 std::list<std::vector<std::string> > test2;
somefunction(test) -> I NEED "list vector string";

How can I do it?

manpreet 2 years ago

I believe that this result can't be achieved via template function specialization (since partial function specializations isn't allowed). But it can be achieved via template class specializations:

#include 
#include 
#include <string>

template <typename T>
struct TypePrinter;

template <typename T>
struct TypePrinter<std::vector<T> >
{
    static std::string print()
    {
        return "vector " + TypePrinter<T>::print();
    }
};

template <typename T>
struct TypePrinter<std::list<T> >
{
    static std::string print()
    {
        return "list " + TypePrinter<T>::print();
    }
};

template <>
struct TypePrinter<std::string>
{
    static std::string print()
    {
        return "string";
    }
};

int main()
{
    std::string i = TypePrinter<std::list<std::string> >::print();
    std::string ii = TypePrinter<std::list<std::vector<std::string> > >::print();
}