# whats wrong with this code?

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[source lang = "cpp"]
#include &lt;iostream&gt;

using namespace std;
double counter (int i)
{
while(i &lt; 100)
++i;
cout &lt;&lt; i &lt;&lt; "\t";
return 0;
}

double counter2 (int i2)
{
while (i2 &lt; 100)
++i2;
i2= i2*i2;
cout &lt;&lt; i2 &lt;&lt; "\t";
return 0;
}

int main()
{
int i = 0;
int i2 =0;

double counter (int i);

double counter2 (int i2);

return 0;
}


im trying to make a program that makes 2 lines. 1st line with numbers from 1-100. 2nd line. numbers from line 1 raised to the 2nd (i^2). when i compile and run it shows nothing on DOS.

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In main(), change:
double counter (int i);double counter2 (int i2)

To:
counter(i);counter2(i2);

The problem is that your code doesn't call the two functions. It just declares them.

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ahh thanks! :)
now, when i run the program, all it writes is :
100 100000

and nothing else. what on earth am i doing wrong here?

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Without more brackets, your while loops only encompass the next line. Just like the functions you've declared, you should enclose everything in a while loop inside of { }. For example:
while (i < 100)//  happens 100 times:++i;// happens once:cout << i;i = 0;while (i < 100){  //  happens 100 times:  ++i;  cout << i;}

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You need braces to group statements under a while. The code:
while(i < 100)  ++i;  cout << i << "\t";

Is equivalent to:
while(i < 100){  ++i;}cout << i << "\t";

This effectively increments i until it's 100 and then prints it. What you presumably meant was:
while(i < 100){  ++i;  cout << i << "\t";}

This will print all of the numbers for you.

HTH

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thanks everyone! :D
heres the final result, not-so-messy (when runned)

[source lang = "cpp"]#include <iostream>using namespace std;double counter (int i) { while(i < 100)  {  ++i;  cout << i << "\t" << i*i << "\n";  }return 0; }int main(){int i = 0;counter(i);return 0;}

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OK, so it works; now, let's make it sensible.

- When you say 'double counter(int i)', you promise that the function will return a value of type double. What is this value supposed to indicate? In the current code, the returned value is always 0 (well, 0.0 - i.e. 0 as a double - because when you say you are returning a double, you return a double, and here that means that the int will be cast to a double implicitly), and never used. This suggests that it actually doesn't mean anything :)

In C++, you don't actually have to return something from a function. You can (and in a case like this, should) declare the return type as 'void', which means you aren't returning anything. At the end of a void function (i.e. a function declared with void return type), control returns implicitly, so there is no need for a return statement (you don't need to specify a value to return, because there is no value). If you need to return from the function before the end, you can just use 'return;'. Trying to specify a return value when the function is declared void is an error, of course. :)

- To do the counting, we increment i each time through the loop, and stop when it reaches a certain value. There is a more specific, and therefore more appropriate construct for this than a while loop: the for loop. Conceptually, this represents the idea that we are doing the loop operations "for" each value of i in range. The bracketed clause after the 'for' keyword contains three items separated by semicolons:

1) An initialization (i.e. a statement executed before the loop starts). This can be used to declare a variable that is scoped to the loop.

2) An exit-condition. At the beginning of each loop, the condition is checked and if not met, the loop is broken. This works just like the bracketed clause for a while loop.

3) A post-loop operation. This action is taken at the end of each iteration of the loop. (If the loop reaches a 'continue' statement, the post-loop operation is still done, so it is *not* quite the same as putting this statement as the last one in a while loop.)

Now, the original code incremented 'i' at the *beginning* of the loop, so we need to make a few modifications to get the original semantics. :)

- Finally, there is never any need to declare a variable to store a value just to pass it to a function. Variables are primarily for storing things that you're going to need *more than once*, or to cut up complex things, or give a name to important sub-results. For simple things like calling a function with some value, you can just pass the value directly.

This gives us:

[source lang = "cpp"]#include <iostream>using namespace std;void counter(int i) {  // The first ++i reflects the fact that the old loop did the increment first.  // The change to <= reflects the fact that we will now test 'i' after  // incrementing it, whereas the old loop tested it before.  // This structure is generally considered cleaner, though: not only are we  // using a more specific construct (the for-loop), but we no longer modify i  // "in the middle of" doing our other stuff; the for loop structure encourages  // us to move all the stuff that happens to our loop counter to the outsides  // of the loop, and the "real work" treats it as read-only.  for (++i; i <= 100; ++i) {    cout << i << "\t" << i*i << "\n";  }}int main() {  counter(0);  return 0;}

We can, of course, go further, but let's digest this much first :)

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wow! thanks alot! that void thing had always been bugging me. When would you use void on main?

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never.

For historical reasons main always returns an int. You see some programs (mostly back in the good old days) programs return a 0 if the program succeeded and some other number (an error code) if there is an error.