C++ class template undefined reference to function

Question

I keep getting undefined reference when i call the two functions from my template class "add" and "greater" in my main function.

So, i have: number.h

#ifndef NUMBER_H
#define NUMBER_H

template <class T>
class number {
public:
    T x;
    T y;

    number (int a, int b){
        x=a; y=b;}
    int add (T&);
    T greater ();
};

#endif

number.cpp

#include "number.h"

template <class T>
int number<T>::add (T& rezAdd){
    rezAdd = x+y;
    return 1;
}

template <class T>
T number<T>::greater (){
        return x>y? x : y;
}

And my main file is: resolver.cpp

#include <stdio.h>
#include <stdlib.h>
#include "number.h"

int main (int argc, char **argv) {
    int aux;
    number<int> c(3,5);

    c.add(aux);
    printf ("number added [%d]\n", c.add(aux));
    printf ("greater number: [%d]\n", c.greater());

    return 0;
}

The errors that i keep getting are:

g++ -Wall -o tema1 resolver.cpp number.cpp
/tmp/ccX483J4.o: In function `main':
resolver.cpp:(.text+0x34): undefined reference to `number<int>::add(int&)'
resolver.cpp:(.text+0x47): undefined reference to `number<int>::add(int&)'
resolver.cpp:(.text+0x64): undefined reference to `number<int>::greater()'
collect2: ld returned 1 exit status
make: *** [all] Error 1

Thanks for the help in advance!

Answer 1

Your class is named wrong. Your class is named cai where all your functions belong to a class named number: http://ideone.com/ZayX0c

One more thing.. you cannot have templates in the .cpp file. Template functions/defintions go in the header along with the class declaration. This is the reason for your undefined function error. Non-template functions go in the .cpp.

#include <cstdio>
#include <cstdlib>

template <class T>
class number {
public:
    T x;
    T y;

    number (int a, int b){
        x=a; y=b;}
    int add (T&);
    T greater ();
};

template <class T>
int number<T>::add (T& rezAdd){
    rezAdd = x+y;
    return 1;
}

template <class T>
T number<T>::greater (){
        return x>y? x : y;
}


int main (int argc, char **argv) {
    int aux;
    number<int> c(3,5);

    c.add(aux);
    printf ("number added [%d]\n", c.add(aux));
    printf ("greater number: [%d]\n", c.greater());

    return 0;
}