How to call in the external function?
 

I have two files and I would like to call addition function from functions.cpp in main.cpp. But I get error:

In function `int main()':
error: `addition' has both `extern' and initializer
error: initializer expression list treated as compound expression
warning: left-hand operand of comma has no effect
error: `addition' cannot be used as a function|
||=== Build finished: 3 errors, 1 warnings ===|

Here are files
main.cpp

#include <iostream>



using namespace std;



int main()

{

    int summation;

    int a, b;

    cout <<"Please Enter the two digits to add"<<endl;

    cin>>a>>b;

    //add external f(x) from function.cpp

    extern int addition(a, b);

    summation = addition(a, b);

    cout<<"The sum is "<<summation;

    return 0;



}

functions.cpp

int addition(int a, int b)

{

    int sum;

    sum = a+b;

    return(sum);

}

Re: How to call in the external function?
 

Add

extern "C++" int addition(int a, int b);

to main.cpp (outside your main function), delete the instruction

external int addition(a, b);

from inside your main function :) ...

main.cpp

#include <iostream>



using namespace std;



// use the external addition function

extern "C++" int addition(int a, int b);



int main()

{

    int summation;

    int a, b;

    cout <<"Please Enter the two digits to add"<<endl;

    cin>>a>>b;

    summation = addition(a, b);

    cout<<"The sum is "<<summation;

    return 0;



}

Now just compile and link them (main.cpp and functions.cpp) togheter ...

Re: How to call in the external function?
 

Great man! I appreciate!