Question

Please have a look at the following code

Calculator.h

#pragma once
#include <iostream>

template<class T>


class Calculator
{
public:
    Calculator(void);
    ~Calculator(void);

    void add(T x, T y)
    {
        cout << (x+y) << endl;
    }

    void min(T x, T y)
    {
        cout << (x-y) << endl;
    }

    void max(T x, T y)
    {
        cout << (x*y) << endl;
    }

    void dev(T x, T y)
    {
        cout << (x/y) << endl;
    }
};

Main.cpp

#include "Calculator.h"

using namespace std;

int main()
{

    Calculator<double> c;
    c.add(23.34,21.56);


    system("pause");
    return 0;
}

When I run this code, I get the below error. I am not much familiar with class templates. Please help!

1>------ Build started: Project: TemplateCalculator, Configuration: Debug Win32 ------
1>LINK : error LNK2001: unresolved external symbol _mainCRTStartup
1>c:\users\yohan\documents\visual studio 2010\Projects\TemplateCalculator\Debug\TemplateCalculator.exe : fatal error LNK1120: 1 unresolved externals
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Answer 1

Threw this into VS2010 really quick. It was not liking cout and endl due to not using namespace std. I just put in a using statement for speed. I prefer to use std:: conventions normally because this avoids naming issues that ‘using’ can generate

Also It complained about no constructor and destructor (added in {}’s)

And like a previous comment said, having your main in a header file is probably bad too. This is all in a default project in test.cpp

EDIT I changed the file structure to have the Calculator in a .h

Calculator.h

template<class T>


class Calculator
{
public:
    Calculator(void)
    {
    }
    ~Calculator(void)
    {
    }

    void add(T x, T y)
    {
        cout << (x+y) << endl;
    }

    void min(T x, T y)
    {
        cout << (x-y) << endl;
    }

    void max(T x, T y)
    {
        cout << (x*y) << endl;
    }

    void dev(T x, T y)
    {
        cout << (x/y) << endl;
    }

private:
    T numbers[2];
};

Test.cpp

// test.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"


#pragma once
#include <iostream>
using namespace std;
#include "Calculator.h"

int main()
{

    Calculator<double> c;
    c.add(23.34,21.56);


    system("pause");
    return 0;
}