Listing 4-25 will not compile

[ITHelpDec]

As it stands, this code will not compile.

Provided the headers are self-explanatory, consider exercising consistency with namespaces (like what can be seen with std::vector<T> and std::future<T>).

Either that or make namespace declarations / directives clear in the example, e.g.

using std::experimental::latch;
// using std::latch since C++20

...or...

using namespace std;