One thing that I have never really properly gotten a handle on is creating comma separated lists of items from a collection. The issue is that the last entry will print a comma: 1, 2, 3, for example. In the past, I would do all kinds of weird code gymnastics to ensure that trailing comma doesn't print, but today I found a wonderful entry on stackoverflow (a rare occurrence for me).

The trick is that you always print the comma, but it's only set as a comma after the first entry. Brilliant!

string sep = "";
for(auto i : items) {
    cout << sep << i;
    sep = ", ";
}

Commit this one to memory.