Adds a helper combinator utils::result_wrap_unpack which, in contrast to
utils::result_wrap, uses futurize_apply instead of futurize_invoke to
call the wrapped callable.
In short, if utils::result_wrap is used to adapt code like this:
f.then([] {})
->
f_result.then(utils::result_wrap([] {}))
Then utils::result_wrap_unpack works for the following case:
f.then_unpack([] (arg1, arg2) {})
->
f_result.then(utils::result_wrap_unpack([] (arg1, arg2) {}))
Adds a utils::result_discard_value, which is an alternative to
future::discard_result which just ignores the "success" value of the
provided result and does not ignore the exception.
Segregates result utilities into:
- result.hh - basic definitions related to results with exception
containers,
- result_combinators.hh - combinators for working with results in
conjunction with futures,
- result_loop.hh - loop-like combinators, currently has only
result_parallel_for_each.
The motivation for the split is:
1. In headers, usually only result.hh will be needed, so no need to
force most .cc files to compile definitions from other files,
2. Less files need to be recompiled when a combinator is added to
result_combinators or result_loop.
As a bonus, `result_with_exception` was moved from `utils::internal` to
just `utils`.
