`thread_pool::task_handle<std::list<T>>` is not defined

[ITHelpDec]

There's no mention of thread_pool::task_handle<std::list<T>> in the book or earlier in the examples until later on.

https://github.com/anthonywilliams/ccia_code_samples/blob/6e7ae1d66dbd2e8f1ad18a5cf5c6d25a37b92388/listings/listing_9.5.cpp#L32

std::future<std::list<T> is used in the book.

.is_ready() also doesn't exist because it looks like it's using an experimental future (see here), which never made it into the standard.