Template class method error "no 'void Pair<T1, T2>::display()' member function Pair declared in class" - class

Question

I'm not sure if my syntax is incorrect. I am getting "no 'void Pair T1, T2::display()' member function Pair declared in class" as well as "no matching function for call to ‘Pair std::basic_string char, std::char_traits char" Here is the header file:
#ifndef PAIR_H
#define PAIR_H
#include <iostream>
#include <string>
using namespace std;
template <typename T1, typename T2 >
class Pair
{
private:
T1 t1;
T2 t2;
public:
Pair(const T1 & t1,const T2 & t2) : t1(t1), t2(t2) {};
T1 getFirst() const { return t1; };
T2 getSecond() const { return t2; };
//setters
void setFirst(const T1 & value) { t1 = value; };
void setSecond(const T2 & value) { t2 = value; };
};
template <typename T1, typename T2>
void Pair<T1,T2> :: display()
{
cout << t1 << " - " << t2 << endl;
}
#endif // PAIR_H
and this is the driver file.
#include <iostream>
#include <string>
using namespace std;
#include "pair.h"
int main()
{
string first;
cout << "Please enter a first name: ";
cin >> first;
string last;
cout << "Please enter a last name: ";
cin >> last;
Pair<string, string> fullName;
fullName.setFirst(first);
fullName.setSecond(last);
cout << "The first name is: " << fullName.getFirst() << endl;
cout << "The last name is: " << fullName.getSecond() << endl;
cout << "The complete pair is: ";
fullName.display();
cout << endl << endl;
int num1;
cout << "Please enter a number: ";
cin >> num1;
int num2;
cout << "Please enter another number: ";
cin >> num2;
Pair<int, int> numbers;
numbers.setFirst(num1);
numbers.setSecond(num2);
cout << "The first number is: " << numbers.getFirst() << endl;
cout << "The second number is: " << numbers.getSecond() << endl;
cout << "The complete pair is: ";
numbers.display();
cout << endl << endl;
string name;
cout << "Please enter a name: ";
cin >> name;
int score;
cout << "Please enter a score: ";
cin >> score;
Pair<string, int> grade;
grade.setFirst(name);
grade.setSecond(score);
cout << "The name is: " << grade.getFirst() << endl;
cout << "The score is: " << grade.getSecond() << endl;
cout << "The complete pair is: ";
grade.display();
cout << endl << endl;
return 0;
}

Answer 1

Yes, your syntax is incorrect.
1) display() is a member of Pair, so you must declare it inside the class.
You can add this declaration line in the public section
void display ();
or you can define display() inside the class (deleting the definition outside) [I added the const modifier]
void display () const { cout << t1 << " - " << t2 << endl; }
1 bis)
I suggest you to define the operator<< (output operator) for class Pair; something like, inside public, this
friend ostream & operator<< (ostream & os, Pair const & p)
{ return os << '(' << p.t1 << ',' << p.t2 << ')'; }
so you can simply output a pair like this
cout << fullName << endl;
2) You don't define a default constructor (without arguments), so you should define you pairs in this way
Pair<string, string> fullName("", "");
Pair<int, int> numbers(0, 0);
Pair<string, int> grade("", 0);
or, avoiding the following setFirst() and setSecond()
Pair<string, string> fullName(first , last);
Pair<int, int> numbers(num1, num2);
Pair<string, int> grade(name, score);
3) I don't know if you know it but there is a standard std::pair class (#include <utility>).
4) You should use che c++ tag for a question like this
5) Sorry for my bad English