Global variables little help pls

[dk_SAM123]

Hi guys I need help with my code this is my homework "Write a C++ program that will calculate the value of “e” (Euler’s number, e = 2.71828…) using a function you create named “find_e”. It shall have no arguments and return no values using the return statement. All transfer of information to and from the function must be in the form of global variables. The function “find_e” must be contained in a file separate file the file containing the “main” function . All output must be from the main program"

I made the program without global variables so you guys can see how it should look
/*#include <iostream>
#include <cmath>


using namespace std;

int main ()

{
double e;
double n;
double accuracy;
int euler = 2.7182818284590452353602874713527;

cout <<"insert the n value "<<endl;
cin>>n;

e=(1+1/n);
e=pow(e,n);


cout<<e<<endl;

accuracy=abs(euler-e);

cout<<"the accuracy is "<<accuracy<<endl;
system ("pause");

return 0;}
*/


and with global variables

this is my function.cpp

#include <iostream>


extern double n;
extern double e;
extern double accuracy;
double euler =2.7182818284590452353602874713527;


void f()
{

e=(1+1/n);
e=pow(e,n);

accuracy=abs(euler-e);

};

*/

and main.cpp

/*
#include <iostream>
#include <cmath>


using namespace std;

double n;
double e;
double accuracy;


int main ()

{


cout <<"insert the n value "<<endl;
cin>>n;


cout<<::e<<endl;



cout<<"the accuracy is "<<::accuracy<<endl;
system ("pause");

return 0;}

*/

I just get a 0 as answer D:

[laserlight]

Just checking: did you teacher stress to you that global variables should be avoided?

I made the program without global variables so you guys can see how it should look

Please post your well formatted code in [code][/code] bbcode tags. Does this program work correctly?

[dk_SAM123]

yes he said we should avoid global variables, but he still wants us to learn how it works
yep the program without global variables works well.

#include <iostream>
#include <cmath>


using namespace std;

int main ()

{
	double e;
	double n;
	double accuracy;
	int euler = 2.7182818284590452353602874713527;

	cout <<"insert the n value "<<endl;
		cin>>n;

		e=(1+1/n);
		e=pow(e,n);


		cout<<e<<endl;

		accuracy=abs(euler-e);

		cout<<"the accuracy is "<<accuracy<<endl;
		system ("pause");

return 0;}

my function.cpp

#include <iostream>


extern double n;
extern double e;
extern double accuracy;
double euler =2.7182818284590452353602874713527;


void f()
{

e=(1+1/n);
e=pow(e,n);

accuracy=abs(euler-e);

};

and my main.cpp

#include <iostream>
#include <cmath>


using namespace std;

double n;
double e;
double accuracy;


int main ()

{


cout <<"insert the n value "<<endl;
cin>>n;


cout<<::e<<endl;



cout<<"the accuracy is "<<::accuracy<<endl;
system ("pause");

return 0;}

[laserlight]

You did not call the find_e function (which you named f) in the main function.

[dk_SAM123]

so would it look like this?

#include <iostream>
#include <cmath>


using namespace std;

 double n;
 double e;
 double accuracy;
 

int main ()

{
	 void f();
	 {double euler =2.7182818284590452353602874713527;

e=(1+1/n);
e=pow(e,n);

accuracy=abs(euler-e);
	 }

cout <<"insert the n value "<<endl;
cin>>n;


cout<<e<<endl;

and function.cpp

#include <iostream>


extern double n;
extern double e;
extern double accuracy;



void f()
{
	double euler =2.7182818284590452353602874713527;

e=(1+1/n);
e=pow(e,n);

accuracy=abs(euler-e);
	
};

[laserlight]

No, call the function in the main function, not define it in the main function. Furthermore, you need to call it at the right place.

[2kaud]

so would it look like this?

No.

In main() you are using n before you have entered it. You are calling f() to calculate euler and update the global variables yet you are also calculating it in main as well?? All main() needs to do is obtain n, call f() and then display the results.

[dk_SAM123]

yeah i knew that was fishy. How do i call f() inside main from another file though? :/

[laserlight]

How do i call f() inside main from another file though?

Declare it before the main function definition, then call it as per normal, e.g.,

void f();

int main()
{
    f();
}

In a larger program, this declaration of f would go into a header fine.

[2kaud]

yeah i knew that was fishy. How do i call f() inside main from another file though? :/

Have a look at http://www.learncpp.com/cpp-tutorial...ultiple-files/ and the following header files section.

[GCDEF]

Your instructions are to call it fine_e. Why are you calling it f?

Your instructions are to calculate e, yet you're initializing a variable with the value you're supposed to calculate. Why?