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What am I doing wrong? (Operator overloading)

This is a discussion on What am I doing wrong? (Operator overloading) within the C++ Programming forums, part of the General Programming Boards category; Code: #ifndef TEST #define TEST using namespace std; template <typename T> class Test { private: T number; public: Test(); Test(T); ...

  1. #1
    Registered User
    Join Date
    Oct 2011
    Posts
    13

    What am I doing wrong? (Operator overloading)

    Code:
    #ifndef TEST
    #define TEST
    using namespace std;
    
    template <typename T>
    class Test
    {
    private:
        T number;
    public:
    Test();
    Test(T);
    template <typename T> friend Test<T> operator+(Test<T> &a, Test<T> &b);
    template <typename T> friend ostream& operator<<(ostream& out, Test<T> &obj);
    };
    
    template <typename T>
    Test<T>::Test(T num1)
    {
        number = num1;
    }
    
    template <typename T>
    Test<T> operator+(Test<T> &a, Test<T> &b)
    {
        return Test<T>(a.number + b.number);
    }
    
    template <typename T>
    ostream& operator<<(ostream& out, Test<T> &obj1)
    {
        out<< obj1.number;
        return out;
    }
    
    #endif
    Code:
    #include <iostream>
    #include "Test.h"
    using namespace std;
    int main()
    {
        Test <int> obj1(5);
        Test <int> obj2(2);
        Test <int> obj3;
    
        obj3 = obj1 + obj2;
        cout << obj3;
        return 0;
    }
    I keep getting an error that says: "LNK2019: unresolved external symbol "public: __thiscall Test<int>::Test<int>(void)" (??0?$Test@H@@QAE@XZ) referenced in function _main"

  2. #2
    Registered User gardhr's Avatar
    Join Date
    Apr 2011
    Posts
    151
    Quote Originally Posted by UserName112 View Post
    Code:
    #ifndef TEST
    #define TEST
    using namespace std;
    
    template <typename T>
    class Test
    {
    private:
        T number;
    public:
    Test();
    Test(T);
    template <typename T> friend Test<T> operator+(Test<T> &a, Test<T> &b);
    template <typename T> friend ostream& operator<<(ostream& out, Test<T> &obj);
    };
    
    template <typename T>
    Test<T>::Test(T num1)
    {
        number = num1;
    }
    
    template <typename T>
    Test<T> operator+(Test<T> &a, Test<T> &b)
    {
        return Test<T>(a.number + b.number);
    }
    
    template <typename T>
    ostream& operator<<(ostream& out, Test<T> &obj1)
    {
        out<< obj1.number;
        return out;
    }
    
    #endif
    Code:
    #include <iostream>
    #include "Test.h"
    using namespace std;
    int main()
    {
        Test <int> obj1(5);
        Test <int> obj2(2);
        Test <int> obj3;
    
        obj3 = obj1 + obj2;
        cout << obj3;
        return 0;
    }
    I keep getting an error that says: "LNK2019: unresolved external symbol "public: __thiscall Test<int>::Test<int>(void)" (??0?$Test@H@@QAE@XZ) referenced in function _main"
    1) You've declared an empty constructor, so define it.
    2) The friend functions can't reuse the template parameter 'T' - name theirs somethings else.
    3) The copy constructor should take a constant reference to 'T'.
    iMalc likes this.

  3. #3
    Registered User
    Join Date
    Oct 2011
    Posts
    13
    Got it. Thanks!

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