Newbie function confusion...

Basicly, the main purpose of a function is to prevent repeated code, right? So, if you have a set of code that your going to use again and again, you put the code into a function, and then just call the function. My problem is with variables - how do you use a common variable in four different functions? Like if your making an rpg, you would probably need the variable Players_Health. If you have four functions that use this variable, how do you have function1 recogonize the change of the Players_Health in function2 without making a new variable each time in each function?

The only way I know to do this is to initilize and declare the variable in no function (at the very top) which is bad practice.

Have you tried declaring parameters?

Even worse are functions that reference global variables, though. Have you used pointers? If not try this:

Code:

void double(int * health){
 *health *= 2;
}
void halve(int * health){
 if(*health)
 *health /= 2;
}

int main(){
int some_health = 12;
cout << "Health: " << some_health << endl;
double(&health);
cout << "Doubled: " <<  some_health << endl;
halve(&health);
cout << "Halved: " << some_health << endl;
cin.get();
return 0;
}

You could use references too which allow you to make permanant changes to the variable but using non-pointer syntax:

Code:

void double(int& health){
 health *= 2;
}
void halve(int& health){
 if(health)
 health /= 2;
}

int main(){
int some_health = 12;
cout << "Health: " << some_health << endl;
double(health);
cout << "Doubled: " <<  some_health << endl;
halve(health);
cout << "Halved: " << some_health << endl;
cin.get();
return 0;
}

Hope that helps...

Oh yeah...reference parameters! Thx sebastiani

Wait a sec...

I have a major function, void Start();. I call it many times because it is like the main part of my program. Well, once I'm close to having 50+ variables Start() uses, I don't want each one to be a reference parameter. So how do I make them reference variables inside Start() without initilizing them, so that when i can call it, i can just simply say Start()?

I would group the 50+ variables into a class or classes, and then pass the class by reference.

If you can't figure any way to group the 50+ variables into a class/es, then I guess you could just store them in a array and then pass that to your function.

No, an array wouldn't really work, and I'm not famililar with classes. Basicly want I want to do something that has the same effect as:

void Start (int &a, int &b, int &c, int &d, int &e....);

without having anything in the parenthesis so that it would look like:

void Start ();

How can I do this?

Make them global then. But remember: it is a very bad practice. Have you ever used a struct? A class is the same thing. And, assuming you are using C++, you can add methods to the struct.

Code:

typedef struct Data {
int a;
int b;
int c;
//...etc
void Start(){
a = b;
b = c;
}
};


int main(){
Data data;
data.Start();
return 0;
}

I wouldn't trust Seb...

He is old...

Originally posted by funkydude9

without having anything in the parenthesis so that it would look like:

void Start ();

How can I do this?

If you really don't want to pass any parameters you could do

Code:

#include//whatever

int a;
int b ;
void Start(){
     //you can use a and b in here

}

int main(){

    //you can also use a and b in here

}

but this is bad progamming practice because it can lead to hard to catch side-effects,

you should start to learn how to use classes.