#ifndef S_LINKED_LIST
#define S_LINKED_LIST

template <typename E>
class SLinkedList;

template <typename E>
class SNode
{
    private:
        E elem;
        SNode<E> * next;
        friend class SLinkedList<E>;
};
template <typename E>
class SLinkedList
{
    private:
        SNode<E> * head;
    public:
        SLinkedList();
        ~SLinkedList();
        bool empty() const;
        const E& front() const;
        void addFront(const E& e);
        void removeFront();
};
#endif /*SLinkedList.h*/

#include "SLinkedList.h"
#include <iostream>

template <typename E>
SLinkedList<E>::SLinkedList():head(NULL){}

template <typename E>
SLinkedList<E>::~SLinkedList()
{while(!empty()) removeFront();}

template <typename E>
bool SLinkedList<E>::empty() const
{return head == NULL;}

template <typename E>
const E& SLinkedList<E>::front() const
{return head->elem;}

template <typename E>
void SLinkedList<E>::addFront(const E& e)
{
    SNode<E> * newNode = new SNode<E>;
    newNode->elem = e;
    newNode->next = head;
    head = newNode;
}

template <typename E>
void SLinkedList<E>::removeFront()
{
    SNode<E> * old = head;
    head = old->next;
    delete old;
}/*SLinkedList.cpp*/

#include <iostream>
#include "SLinkedList.h"

int main()
{
    SLinkedList<std::string> newlist;
    newlist.addFront("MSP");
    std::cout << newlist.front();
    return 0;
}/*test_slinkedlist.cpp*/

Undefined symbols for architecture x86_64:
...
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)