Some of the code in this section is admittedly complicated. We wrote an operator<< implementation for tuples, which looks very complex but supports all kinds of tuples that themselves consist of printable types. Then we implemented the sum_min_max_avg function, which just returns a tuple. Another very complicated thing to get our head around was the function zip.

The easiest part was sum_min_max_avg. The point about it is that when we define a function that returns an instance tuple<Foo, Bar, Baz> f(), we can just write return {foo_instance, bar_instance, baz_instance}; in that function to construct such a tuple. If you have trouble understanding the STL algorithms we used in the sum_min_max_avg function, then you might want to have a look at the Chapter 22, STL Algorithm Basics of this book, where we already had a closer look at them.

The other code was so complicated that we dedicate the specific helpers their own subsections: