`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.

ccia_code_samples/listings/listing_9.5.cpp

Line 32 in 6e7ae1d

thread_pool::task_handle<std::list<T> > new_lower=

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.