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<p>Getting to ditch a similar connotation in do notation is exactly
why I've started this thread, of course! Some instances are far
less about having pure/return, at least without some more powerful
constructs we can't have in a standardised Haskell just yet. It's
maybe a personal irritation that ApplicativeDo outright fails in
that situation.<br>
</p>
<p>I was slightly appalled when I realised just now what
pronunciations of *> and <* I could most easily justify if
nobody else comes up with a suggestion - I think <* might be
"klap".</p>
<p>I do think there's value in wondering whether there are small
changes to GHC we might request if nobody else does it. But that's
partly because the Report has to be descriptive by default -
otherwise there's no good institutional eye on neatening things up
over time that has an eye on standards rather than the concerns
that drive GHC.</p>
<p>Fundamentally, if I'd wanted to drag up MRP rather than round off
an edge, I would've done so explicitly! If someone wants to tell
me where to nag the GHC folks I guess I might find the time. But
I'm definitely looking at removing warts in the context of things
that are already happening myself.<br>
</p>
<div class="moz-cite-prefix">On 18/12/2018 14:52, Cale Gibbard
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAF3RzK-bTm3Zge5TTxNPOmFYiwJuBj07MHn8QSaZQ-pM1rcm8Q@mail.gmail.com">
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Is it just me, or is all the discussion in these threads much more
easily resolved if the Report is simply a report? Describe what
is, rather than what you wish it was, and there's much less room
for disagreement. A future Report can describe the way that these
things work differently in the future when the changes actually
happen in the implementation(s).
<div><br>
</div>
<div>I don't know about anyone else, but at least from my
perspective the value of the Report is in being valid
documentation. The extent to which it fails to describe the
actual family of languages we're presently writing code in is
the extent to which it is failing to be a useful resource for
our daily lives. </div>
<div><br>
</div>
<div>I dunno, I feel kind of strange when people talk about
removing 'return' for example, since it's very unlikely to go
anywhere any time soon given how much code it is referenced in.
It would be practically unreasonable even to try to deprecate
it. Given that the Report is going to discuss this part of the
language, it makes sense that it should be documented. </div>
<div><br>
</div>
<div>Secondarily, it's a bit hard to describe why this is, but I
personally find it a bit obnoxious whenever someone uses 'pure'
rather than 'return' if the functor is known to be an instance
of Monad and the generality isn't needed. It's a kind of signal
that the code we're writing is (and perhaps needs to be)
Applicative-polymorphic, or that we lack a Monad instance. So
when I see it, I'm forced to consider for a moment why that
might be, and whether I've understood the context incorrectly
(and if it's not the case, that's sort of irritating).</div>
<div><br>
</div>
<div>So when I see a suggestion to remove 'return' altogether it's
sort of like "let's make everything mildly annoying to read
forever" (by forcing this thought about exactly how general the
code is, and making it slightly harder to guess the types at a
glance).</div>
<div><br>
</div>
<div>It's like while pure and return are equal whenever they would
both typecheck, they've come to have very different connotations
about the surrounding code. </div>
<div><br>
<div class="gmail_quote">
<div dir="ltr">On Tue, Dec 18, 2018, 05:42 Philippa Cowderoy,
<<a href="mailto:flippa@flippac.org"
moz-do-not-send="true">flippa@flippac.org</a>> wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">I'm having
a moment of fail trying to work out how to leave a comment.<br>
<br>
Is there a reason (other than GHC not doing it yet) not to
have do <br>
notation use *> instead of >> in line with using
the least restrictive <br>
function? I have some otherwise-nice logic programming code
that would <br>
actively benefit from it and it seems like a missing step
from here.<br>
<br>
On 15/12/2018 23:46, Mario Blažević wrote:<br>
> The very first RFC created (<a
href="https://github.com/haskell/rfcs/pull/1"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://github.com/haskell/rfcs/pull/1</a>),
<br>
> the Applicative/Monad Proposal, has now reached the
Last Call stage. <br>
> In order to ground the discussion, I have taken some
time to update <br>
> the Prelude and the text of the Haskell Report with its
effects before <br>
> the call. The rendered report is available at <br>
> <a
href="https://github.com/blamario/rfcs/blob/amp/report/report/haskell.pdf"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://github.com/blamario/rfcs/blob/amp/report/report/haskell.pdf</a>
<br>
> for your review.<br>
><br>
><br>
> TL;DR:<br>
><br>
> The proposed changes to the report add the latest
design of the <br>
> Applicative and Alternative classes, but otherwise are
intentionally <br>
> minimal. Any further modifications, like the MonadFail
proposal or <br>
> moving return out of the Monad class, should be
relegated to new RFCs.<br>
><br>
><br>
> In some more detail, the changes are:<br>
><br>
> 1. Applicative has been added as a subclass of Functor
and superclass <br>
> of Monad, its methods and laws as currently defined in
the base <br>
> library. The class and all its methods (pure,
(<*>), (<*), (*>), and <br>
> liftA2) are exported from Prelude, but no other
Applicative-related <br>
> functions (like liftA3) are.<br>
><br>
> 2. The Functor class definition has been moved from
module <br>
> Control.Monad to Control.Applicative in order to avoid
circular <br>
> imports. Note that neither module is a part of the
language <br>
> specification.<br>
><br>
> 3. The Monad class has been left unmodified, apart from
making <br>
> Applicative its superclass and adding return a == pure
a as a law.<br>
><br>
> 4. Alternative has been added to the
Control.Applicative module, but <br>
> not to Prelude. This is the same treatment already
meted to MonadPlus. <br>
> I'm unsure why MonadPlus even exists in the report, as
it has no <br>
> relevance to the language specification, and I would
gladly remove <br>
> both classes.<br>
><br>
><br>
> Please take some time within the following three weeks
(including some <br>
> extra allowance for the upcoming holiday breaks) to
vote for or <br>
> against the proposal, or to leave a comment with
suggestions for its <br>
> improvement.<br>
><br>
><br>
> _______________________________________________<br>
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</blockquote>
</div>
</div>
</blockquote>
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