How do I make a function that resets a while loop? - c++

Question

I have made a program that outputs 0 3 6 9 12. Now, I want to make a function called reset() that resets the program, so it outputs the same numbers after 12. How do I do that?
#include <iostream>
using namespace std;
void byThrees();
void reset();
int i = 0;
int main()
{
byThrees();
return 0;
}
void byThrees()
{
while(i<13) {
cout << i << ' ';
i += 3;
}
}
void reset()
{
}

Answer 1

Don't use global variables when you can avoid it! And right now, you can avoid it.
No one else wants to use i except byThrees(). And it sounds like you don't want the value of i to persist across runs of byThrees(). So just make it a local variable in the function:
void byThrees()
{
int i = 0;
while(i<13) {
cout << i << ' ';
i += 3;
}
}
Now whenever you want to print your 0, 3, 6, 9, ... series, just call byThrees():
int main() {
byThrees();
std::cout << std::endl; // Add a newline between runs
byThrees();
return 0;
}

Answer 2

Another method to do it, if you want to save memory and just keep one global variable (at least I think this saves memory) is:
#include <iostream>
using namespace std;
int i = 0;
int main()
{
run(); // this function both resets i to 0 and runs byThrees()
return 0;
}
void byThrees()
{
while(i < 13) {
cout << i << ' ';
i += 3;
}
}
void run()
{
i = 0;
byThrees();
}
Basically, whenever you run the function run(), your code will reset the global variable i to 0 and run byThrees() with i being 0 initially. This means that you can repeatedly call run() in your code and every time it will output 0 3 6 9 12.
If what you mean in your post is that you want your code to output 0 3 6 9 12 and then 15 18 21 24 27 on the next call (and so on), you could do something like this:
#include <iostream>
using namespace std;
int i = 0, nextI = 0; // nextI is a variable that stores the next starting position of i
int main()
{
run(); // will output "0 3 6 9 12"
run(); // will output "15 18 21 24 27"
run(); // will output "30 33 36 39 42"
return 0;
}
void byThrees()
{
while(i < nextI + 13) {
cout << i << ' ';
i += 3;
}
nextI += 15; // increases nextI for the next time "run()" is called
}
void run()
{
i = nextI;
byThrees();
}
This code basically keeps track of where the list of numbers left off and continues from there.