MRP, 3-year-support-window, and the non-requirement of CPP (was: [Haskell-cafe] Monad of no `return` Proposal (MRP): Moving `return` out of `Monad`)

[Johan Tibell]

(Resending with smaller recipient list to avoid getting stuck in the
moderator queue.)

On Tue, Oct 6, 2015 at 9:10 AM, Herbert Valerio Riedel <hvr at gnu.org> wrote:

> On 2015-10-05 at 21:01:16 +0200, Johan Tibell wrote:
> > On the libraries I maintain and have a copy of on my computer right now:
> 329
>
>
> Although this was already pointed out to you in a response to a Tweet of
> yours, I'd like to expand on this here to clarify:
>
>
> You say that you stick to the 3-major-ghc-release support-window
> convention for your libraries. This is good, because then you don't need
> any CPP at all! Here's why:
>
> [...]
>

So what do I have to write today to have my Monad instances be:

 * Warning free - Warnings are useful. Turning them off or having spurious
warnings both contribute to bugs.
 * Use imports that either are qualified or have explicit import lists -
Unqualified imports makes code more likely to break when dependencies add
exports.
 * Don't use CPP.

Neither AMP or MRP includes a recipe for this in their proposal. AMP got
one post-facto on the Wiki. It turns out that the workaround there didn't
work (we tried it in Cabal and it conflicted with one of the above
requirements.)

PS: I'm a bit disappointed you seem to dismiss this proposal right away
>     categorically without giving us a chance to address your
>     concerns. The proposal is not a rigid all-or-nothing thing that
>     can't be tweaked and revised.  That's why we're having these
>     proposal-discussions in the first place (rather than doing blind
>     +1/-1 polls), so we can hear everyone out and try to maximise the
>     agreement (even if we will never reach 100% consensus on any
>     proposal).
>
>     So please, keep on discussing!
>

The problem by discussions is that they are done between two groups with
quite a difference in experience. On one hand you have people like Bryan,
who have considerable contributions to the Haskell ecosystem and much
experience in large scale software development (e.g. from Facebook). On the
other hand you have people who don't. That's okay. We've all been at the
latter group at some point of our career.

What's frustrating is that people don't take a step bad and realize that
they might be in the latter group and should perhaps listen to those in the
former. This doesn't happen, instead we get lots of "C++ and Java so bad
and we don't want to be like them." Haskell is not at risk of becoming C++
or Java (which are a large improvement compared to the languages came
before them). We're at risk of missing our window of opportunity. I think
that would be a shame, as I think Haskell is a step forward compared to
those languages and I would like to see more software that used be written
in Haskell.

We've been through this many times before on the libraries list. I'm not
going to win an argument on this mailing list. Between maintaining
libraries you all use and managing a largish team at Google, I don't have
much time for a discussion which approaches a hundred emails and is won by
virtue of having lots of time to write emails.

-- Johan
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/haskell-prime/attachments/20151006/1981f347/attachment.html>