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Subject: Re: [boost] [outcome] Feedback on parts A and B of Tutorial mk III requested
From: Asbjørn (lordcrc_at_[hidden])
Date: 2017-01-30 13:20:50

On 30.01.2017 11:19, Niall Douglas wrote:
> I am truly hoping that this will be the last time I ask for feedback on
> Outcome's tutorial as this is the third complete rewrite. Many thanks
> for all the feedback so far, this Mk. III tutorial wouldn't look like
> this without all your help.

Just some semi-random comments from a "plain" Boost user, who also read the
initial version of the docs.

The current form is much better than the initial version. It was easier to skip
the parts that I do not care much about, and easier to follow what the goal of
the library was. As someone who hasn't read anything about expected<T,E> before,
it was nice to have a section on it.

I overall liked the code examples, they worked much better for me than the
previous ones.

However I do think the name "Tutorial" is a bit of a misnomer, and the parts A,
B and C should be renamed to "Background", "Rationale" and "Introduction"
respectively (or something similar). Most of part C is introducing the API, and
the full tutorial bits, when ready, really should stand out a bit more compared
to the current A, B and C sections.

In part B I think you should drop the inlined list of std:errc members, instead
linking to it somewhere. Then you could simply write:

"The third reason is that the C++ 11 standard library already provides an enum
of the most common error codes for you. It's called std::errc and it has the
standard POSIX error codes. Most of the time you'll find that whatever custom
error code domain you may want to write can be adequately covered by std::errc.
In fact, let's try it:"

The list, while a useful reference, adds to the "wall of text" feeling that part
B already suffers a bit from.

Going back to the start, I think rephrasing the initial portion of the
description section to focus on Outcome rather than expected<T, E> would be
beneficial. As it reads now, I still come away from this thinking it's a helper
library to expected<T, E>, rather than something that could very well be used on
its own.

Just an example:

"This is the Outcome library. It' a Boost C++ 14 library intended for
ultra-lightweight error handling in large C++ codebases, providing a more
expressive and type safe alternative to integer error codes or enums.

Unlike alternative implementations, it works perfectly with exceptions and RTTI
disabled and is thus suitable for low-latency/games/finance/SG14 users. One
could view Outcome as a minimum overhead universal outcome transport mechanism
for C++, hence being named "Outcome".

The Outcome library provides an implementation of expected<T, E> (which is on
the C++ 20 standardisation track), with the expected<T, E> refinements
outcome<T> and result<T>."

Now I'm just a n00b, but I get worried about the raw char*'s everywhere. I know
you're aiming for maximum speed, but couldn't the interface have std:string
overloads as a safer alternative? At least for things like
error_code_extended::extended_message(). I don't generally care much for the
brute-force performance of my error handling code, it's not the hot path.

Personally I like that you've removed the word "monad" for most of the
documentation. It's one of those concepts I sorta know what is, but I still have
to do a web search each time just to remind me. Though in part C one is
introduced to monad_error and friends. Now, _I don't mind this_, however I think
it would be nice to have a _footnote_ here to quickly explain where the name
comes from, with a link to some page with more info on monads.

Anyway, I now got a much better impression of what this library is about than
the initial version of the docs. It also presented Outcome as a useful and
interesting library, and as something I would want to try.

- Asbjørn

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