Not working array loop

Question

Why is this not working. I Just want loading like effects. I just compiled the code the g++ compiler. It take time and just print * * * B R E A K * * *. There is no difference between per letter.

#include <iostream>
using namespace std;

int main()
{
    int wait = 1000000000;
    char text[] = {"* * * B R E A K * * *"};

    for(int i = 0; i < 21; i++)
    {
        cout << text[i];

        for(int j = 0; j < wait; j++)
            ;
    }
}

Why do you expect that there will be "difference between per letter"? — Soren
– Soren, Commented Aug 25, 2015 at 14:30
It appears to work as designed. What are you trying to do differently? — Bob Dylan
– Bob Dylan, Commented Aug 25, 2015 at 14:31
You can't rely on the second loop waiting at all, the whole thing could be optimized out. — TartanLlama
– TartanLlama, Commented Aug 25, 2015 at 14:32
Use some sort of timer to do the pause, the empty loop can be completely optimized out by an optimizing compiler. Also prefer std::string over char text[], it will make your life a lot easier. — shuttle87
– shuttle87, Commented Aug 25, 2015 at 14:34

Soren · Accepted Answer · 2015-08-25 14:39:12Z

6

Your wait loop is likely optimized out from the code because the compiler can see that it has no effect. Try to do a nano-sleep instead, like

#include <iostream>
#include <unistd.h>

using namespace std; 
int main()
{
   char text[]={"* * * B R E A K * * *"};
   for(int i=0;i<21;i++)
   {
      cerr<<text[i];
      usleep(100000);
   }
}

Also, std::cout is buffered, which means that it will not write until there is a newline, program terminates or you flush -- for simplicity change the cout to cerr which is non-buffered....

edited Aug 25, 2015 at 14:39

answered Aug 25, 2015 at 14:33

Soren

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1 Comment

deaddroid Over a year ago

Thanks.. Maybe I can also flush the buffer using manipulator cout <<flush or cout.flush()

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