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Subject: Re: [boost] [Boost-announce] [Hana] Formal review for Hana next week (June 10th)
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2015-06-16 20:35:41

On 5 Jun 2015 at 16:57, Glen Fernandes wrote:

> - Whether you believe the library should be accepted into Boost

I vote unconditional acceptance.

> - Your name

Niall Douglas.

> - Your knowledge of the problem domain.

Very little. Moreover, the type of C++ programming used in its
implementation I find a major chore to write, and a lot of it is
frankly beyond me (as you'll see in my shortly to presented optimally
lightweight monad<T>). I am particularly hoping that Hana will
eventually free me of ever having to do it by hand again in the
future once Visual Studio can compile Hana.

> You are strongly encouraged to also provide additional information:
> - What is your evaluation of the library's:
> * Design

There is a still a bit to go to match STL naming conventions, though
it has improved enormously over before. For example, the STL uses
empty(), not is_empty(). is_empty() in the STL means something

I'd also *hugely* prefer if Hana matched, name for name, the name
choices in Ranges v3. For example, it's group() in Hana, but
group_by() in Ranges v3. That would lessen the cognitive load for
people using both together - which I suspect in the longer term will
be many if not most. It also would increase the chances of Hana
entering the standard C++ library as a compile-time version of

It also provides a way of telling the naming bike shedders to sod
off, as whatever Eric has chosen is what you'll choose period.

I also think all the Concepts need to match naming with Eric's, and
eventually in the future that both libraries use identical Concept
implementations (which I assume would then be upgraded with Concepts
Lite on supporting compilers). I'd suggest therefore breaking the
Concepts stuff out into a modular part easily replaceable in the
future with a new library shared by Hana and Ranges.

> * Implementation

I won't comment on this as I am not really qualified to say. It looks

> * Documentation

I agree with other reviewers that the code examples need a hana::
namespace qualifier before all uses of hana stuff.

I quite like the doxygen prettification, maybe matching the Boost
colour scheme more? One problem is slow page load times on IE,
especially the first page, but also every click in the left hand
table of contents. I also see no graphs displaying either in IE or

BTW for my lightweight monad<T> I have some python which counts x64
ops generated by a code example and gets the CI commit to fail if
limits are exceeded, if you're interested for the benchmarking and/or
making hard promises about runtime costs.

> * Tests

Tests should be capable of using BOOST_CHECK and BOOST_REQUIRE as
well as static_assert. It should be switchable. You can then feed the
Boost.Test XML results into the regression test tooling.

> * Usefulness

Very useful.

> - Did you attempt to use the library? If so:
> * Which compiler(s)?
> * What was the experience? Any problems?


> - How much effort did you put into your evaluation of the review?

I've been reviewing the project for over a year now regularly, and
have been known to write Louis private emails with ideas :)


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