Re: [boost] [review] Review of Outcome (starts Fri-19-May)

Le 23/05/2017 à 12:35, Andrzej Krzemienski via Boost a écrit :

2017-05-23 8:50 GMT+02:00 Andrzej Krzemienski :

...

2017-05-23 1:56 GMT+02:00 Jared Wyles via Boost :

...

Hello,

One of the questions that is inevitably asked when a proposal to switch to using something like outcome is that of exceptions. Why outcome over exceptions etc which you briefly touch on in your ACUU talk. With that in mind, when attempting to sell this library having the motivating example on the boost.outcome docs using exceptions really makes starting the discussion harder. I understand one can never escape exceptions, but it shouldn't be used as the first example a new user sees. I would like to see this example updated to show how to handle errors with out the need for exception handling around accessing *value*. Personally, I see something similar to https://ned14.github.io/boost.outcome/md_doc_md_03-tutorial_ b.html#expected_payload as a much better example to help sell outcome and therefore better suited as the motivating example for the front page of the docs.

This means, the initial example should use `boost::outcome::result` (instead of `boost::outcome::outcome`). And then function that inspects the result could read:

``` void test() { if (auto r = fun) use_int_value(r.value()); else inspect_error_code(r.error()); } ```

The initial example could look like this: https://github.com/akrzemi1/__sandbox__/blob/master/outcome_intro.md

THis is a better example of what Outcome can do, yes. Would the following works as well? I have changed just outcome by expected. What if fun returns an expection ptr? auto my_fun()noexcept -> outcome::expected<int> { std::error_code ec; int i =Library1::fun(ec); if (ec) return outcome::make_errored_outcome(ec);// error code returned inside outcome BOOST_OUTCOME_TRY(rslt2,Library2::fun());// if fun() succeeds, rslt2 of type int contains result // otherwise returns the result of fun() up BOOST_OUTCOME_TRY(rslt3,Library3::fun());// Similarly, either rslt3 is an int with successful result, // or my_fun() returns what Library3::fun() has returned return i + rslt3;// return a result with a value }; Best, Vicente