title: How do I "clear" std::promise?
body: <p>I have a program, which should in cycle launch 8 threads, which will return a value using <code>std::promise</code>. So I think I need to create a vector of 8 <code>promise</code> objects, get their <code>future</code>s, and use these <code>promise</code>s to return the values and then <code>join</code> the threads with <code>main</code>. The problem is this: on the next iteration I will create 8 more threads -- can i reuse the same <code>promise</code> objects, or do I need to create 8 more? I haven't found any way to reuse them on the internet, but maybe I'm missing something obvious?</p>