void?

i was reading a tutorial and it was about classes. They declare sum things, well ill paste it

Code:

---

class Dog {
public:
    void setAge(int age);
    int getAge();
    void setWeight(int weight);
    int getWeight();
    void speak();
private:
    int age;
    int weight;
};

---

well wat does the void before setage and setweight mean?

It means the function is not returning a value.

so wat r u sayin, i can set sumthin but i cant output it on da screen?

No what he is saying is that the function does not return a value eg

Code:

---

int foo()
{
  return 1;
}
void bar()
{
  cout<<"Hello";
}

---

i know, im a dumbass! but plz explain better

OK when you have a function it has to be a type int,float,char,or void or some other value. void does not return a value. You can think of it like this.

Code:

---

#include <iostream>

int add(int a,int b);
float divide(int a,int b);
void printStuff(int a,int b);

int main(void)
{
  int addResults = add(10,5);//This is setting the variable addResults to the return of the function add()
  float divideResults = divide(9,4);//doing the same as the first but with divide
  std::cout<<addResults<<std::endl;
  std::cout<<divideResults<<std::endl;
  printStuff(10,10);//this will do whats in the funtion
  std::cin.get();
  return 0;
}

int add(int a,int b)
{
  return (a+b);
}
float divide(int a,int b)
{
  return (a/b);
}
void printStuff(int a,int b)
{
  std::cout<<"a equals: "<<a<<std::endl;
  std::cout<<"b equald: "<<b<<std::endl;
  //notice it doesn't return a value!
}

---

u guys a really confusing sumtimes

What are you confused about? i don't know any other way of explaining it to you if you can't get such a simple concept maybe look into a different thing to pass your time

just explain wat u mean by returning a value

Just as it sounds a function RETURNS A VALUE

Code:

---


int blah()
{
  return 1;//THIS FUNCTION RETURNS 1!!!!!!!!!!!
}
float meh()
{
  return 4.5//THIS FUNCTION RETURN 4.5!!!!!!!!!!!
}
int main(void)
{
  weee=blah();//THIS EQUALS 1 BECAUSE blah() RETURNS 1!!!!!!!!!!!!!!!
  yeppers=meh();//THIS EQUALS 4.5 BECAUSE meh() RETURNS 4.5!!!!!!!!!!!!
  return 0;//MAIN RETURNS 0!!!!!!!!
}

---

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! just for some extra effect

thankyou, was that so hard?

No, but is understanding what return means so hard?

it is wen crappy tutorials dont explain , i still dont get it but i aint askin no more, but dont make me come over there biatch(kiddin)

Hi polonyman,

I'm also really new to C++ (and new to the boards here). I found functions a little bit tricky at first too. As a test of how well I understand them let me try and give you my two cents. If I'm wrong, then I'll be glad to hear so from the more experienced folk here.

I think of functions as kinda like a really big variable, but a variable that does something. You can put stuff in it (arguments) and get stuff out of it (return) if you choose to . You have to tell it, though, what kind of arguments you want it to accept as well as what kind of value to spit back out (return). It spits back the return value at the point where you called the function (usually, I guess, in main, but I suppose it could be called from another function just as easily?).

The void in front of the function means that you don't want it to return any value.

You can still output to the screen from a function (for ex. with cout) but this is different than returning a value.

Does this sound right?

It actually makes me think just a bit about the return value of main. If functions return their values to main (or some other place within the program) where does main return its value to? My first inclination would be that it returns either to the compiler or to the OS. But I can't be sure of that.

Anyway, don't know if this helps at all, but hope you can get it sorted out.

it (one function) could be called from another function just as easily?-----Yes, one function can be call from another and return to calling.

it (main()) returns either to the compiler or to the OS---main() returns a value to the OS. What the OS does with the return value is up to the OS.

A challenge, just for fun:
Make a function that behaves exactly like a variable.

Here is the simplest way I know to explain return.

Code:

---


// Function that wont return anything
void Function ()
{

    // Do stuff

}

// Function that would actually return a value.
int ReturnMe ()
{

    int number = 5;
 
    return number;

}

// now if I do this

int value;
value = ReturnMe ();

// value now equals 5

---

This guy sounds like a troll to me...

Quote:

---

Originally Posted by MortalMonkey

A challenge, just for fun:
Make a function that behaves exactly like a variable.

---

I love a good challenge so here goes (if this is a trick question though, I'll feel really dumb :eek: ):

A variable stores a value so all it seems we need is a function that mimics this, ie. returns an inputed value. My first idea was something very simple like this:

Code:

---

int imaVariable(int x)
{
    return x;
}

---

But I can already see some problems with this too simple idea. A global variable (for example) would stay in scope for the whole duration of the program's running time. As long as you don't change it the value of the variable stays the same the whole time. This function, however, would have to be filled with a value every time you called it. Kinda defeats the purpose of using a variable to store stuff. We would need a function that would ask for a value once and then retain it so that when you call it again you don't have to pass it arguements.

My second idea was to make a function that takes no arguments but asks for input and returns that input:

Code:

---

int imaVariable(void)
{
    int value;
    cout<<"Enter value: "<<endl;
    cin>>value;
    return value;
}

---

But again, the same problem... every time you call the function, you have to input the value.

My last idea was to simply assign a value to the function:

Code:

---

int imaVariable(void)
{
    return //value I want to assign the function goes here;
}

---

But this seems more like a constant than a variable to me so... I don't know...


Can such a function be created? At this point I don't know.

I've seen some amazing stuff on this board already so I won't be surprised if someone more experienced here can do it, but at this point in my study I don't think I can.

At any rate, thanks for the brain bender (well, brain bender for a noob like me). It's given me something to think about. Perhaps a function is like a temporary variable that does something.

[edit]

Bah, never mind :rolleyes:

You would almost have to use a global variable.

I cant think of anyother way.

I was originally going to do the following:

Code:

---

namespace {int var;}
int imavariable()
{
  return var;
}
void imavariable(int x)
{
  var = x;
}

---

However, that doesn't work since it takes no consideration of scope - and besides which, you cannot take the address of the variable and you cannot use the assignment operator, or other such variable syntaxes.

Code:

---

#include <iostream>
using namespace std;
                                                                               
int& Var(void) {
        static int var = 0;
        return var;
}
                                                                               
int main(void) {
        cin >> Var();
        Var()++;
        cout << Var() << endl;
        return 0;
}

---

Doh. I was, uh.. just about to post that.. yeah. :rolleyes: