CODEWITHSUNDEEP
c++templates
Dina Benyamin
Dina Benyamin

Reputation: 97

Extracting template arguments' value

I have this class:

#include <iostream>

template<typename T, typename... TT>
class List
{
public:
    typedef T head;
    typedef List<TT...> next;
    enum { size = sizeof...(TT)+1 };
};

and this main:

#include <iostream>
#include "List.h"
using namespace std;

template <int T>
struct Int {
    enum { value = T };
};

int main() {
    typedef List<Int<1>, Int<2>, Int<3>> list;
    cout << list::template head.value << endl; // Error
    cout << list::size; // Works
    return 0;
}

Error message:

error: expected primary-expression before '.' token
     cout << list::template head.value << endl;

I would appreciate any help.. I've been trying to solve this for the past half hour and this is probably something very stupid that I just can't put my finger on.

Upvotes: 0

Views: 45

Answers (1)

Quentin
Quentin

Reputation: 63154

head is a type. That means that you can't disambiguate it with template, nor can you access it with .. There's not much to do to fix it:

std::cout << list::head::value << std::endl;

Also, please get rid of the using namespace std;.

Upvotes: 4

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