Two Semicolons

[Fransje]

Hi all!

I was reading through some questions on the General C++ Thread, and I came across the following code, from which I don't understand the two ;;'s:

#include <thread>
#include <chrono>
void fn()
{
    for(;;)
   {
        std::this_thread::sleep_for(std::chrono::seconds(1));
        // <-- call your function here
   }
}
int main()
{
    std::thread(fn).detach();
    // <- do something that takes more than a second here
}

Can anybody explain how this can be correct?
Thanks in advance!

[zb0S216C]

Two adjacent semi-colons in a for loop is considered to be an infinite loop; it's equivalent to:

while(true)
{
    // ...
}

_Wazzak

[Athar]

See here for the general structure of a for loop:
http://www.cplusplus.com/doc/tutorial/control/#for

When the condition part is left empty, it is implicitly true.

[Fransje]

Thanks! I understand!