I'm too voting in favor of the proposal in the current form. Unsure about
the parens, but looking forward to some way of replacing reduce_while with
some version of the for.
Best,
Stefan
wt., 21 gru 2021 o 21:47 Christopher Keele <christheke...@gmail.com>
napisał(a):
> *Guides Feedback*
>
> These look excellent, should make the power of *for* much more accessible.
>
> *let Feedback*
>
> I like the functionality of this proposal much more!
>
> I will say, I'm still not a fan of using new qualifiers. I'm not sure why
> we need to introduce a new special form for this, since we can do whatever
> we need to in the macro? What's wrong with:
>
> > for count = 0, count < 5, x <- element do {x, count + 1} end
>
> Perfectly matches traditional for loops, and pattern matching in function
> arguments, with all the familiar errors/warning possibly emitted from
> them, while keeping the bodies identically functionally-refactorable. No
> *let*s needed.
>
> Re:* for reduce*, since *for* already has idiomatic keyword arguments to
> further modify functionality, isn't *:reduce* is doing fine as is? We'd
> just document how it interacts with for-bindings.
>
> > Furthermore, the introduction of let and reduce qualifiers opens up the
> option for new qualifiers in the future, such as for async that is built on
> top of Task.async_stream/3.
> >
> > Async doesn't have its own arguments
> <https://gist.github.com/josevalim/fe6b0bcc728539a5adf9b2821bd4a0f5#naming>
>
> Similarly, I'm unsure what's wrong with add an *async: true* keyword
> argument. It's just behaviour configuration, not something we need to bring
> to the forefront as a pattern match?
>
> *Replies*
>
> > I am against the notion of `for_let` and `for_reduce`. I see that as
> using up more of the special forms "namespace".
>
> Agreed, mirroring my misgivings about "for let" and "for reduce".
> On Tuesday, December 21, 2021 at 11:58:19 AM UTC-5 gva...@gmail.com wrote:
>
>> I'm a vote in favor of the proposal. I think I have a slight preference
>> for the parens. But it's very slight, and I'm not sure I wouldn't change my
>> mind after using it for a while.
>>
>> I am against the notion of `for_let` and `for_reduce`. I see that as
>> using up more of the special forms "namespace".
>>
>> I'm slightly disappointed that the old style `reduce:` option will be
>> deprecated (because I have old code I'll have to update) however, the
>> change does make things more consistent and I appreciate the thought about
>> future extensions to for comprehensions.
>>
>> -Greg Vaughn
>>
>> PS. I just watched your latest Twitch stream. I wish I could have been
>> there live to hear you read the dictionary and to offer obscure English
>> words to the bikeshed discussion :-D
>>
>> On Dec 21, 2021, at 3:31 AM, José Valim <jose....@dashbit.co> wrote:
>>
>> Compared to the previous proposal, this one has been very quiet so far.
>> :) I am unsure if it was because it was a Monday or because holidays are
>> coming, so I am sending a ping.
>>
>> ALso note I updated the proposal to not use parens around let/reduce,
>> which seems to be the preference so far:
>> https://gist.github.com/josevalim/fe6b0bcc728539a5adf9b2821bd4a0f5
>>
>> On Tue, Dec 21, 2021 at 1:29 AM 'eksperimental' via elixir-lang-core <
>> elixir-l...@googlegroups.com> wrote:
>>
>>> Not necessarily that they are replaceable,
>>> but that pattern of :cont, :halt, :suspend is most commonly used via
>>> Enumerable.reduce
>>>
>>>
>>> On Mon, 20 Dec 2021 19:18:53 -0500
>>> "'eksperimental' via elixir-lang-core"
>>> <elixir-l...@googlegroups.com> wrote:
>>>
>>> > > I have found only one usage of Enum.reduce_while in Elixir's
>>> > > codebase.
>>> >
>>> > This is because under the hood Enum.reduce_while is a call
>>> > `Enumerable.reduce/3`, so we are invoking this functions direcly.
>>>
>>> >
>>> > On Tue, 21 Dec 2021 00:47:44 +0100
>>> > Stefan Chrobot <ste...@chrobot.io> wrote:
>>> >
>>> > > Thanks, that version would work, but agreed - not sure how big of an
>>> > > improvement that would be over Enum.reduce_while. Trying to think
>>> > > about this in a more imperative style, it seems that maybe an
>>> > > equivalent of break is what I'm after? Maybe something close to
>>> > > Ecto's Repo.transaction semantics?
>>> > >
>>> > > for foo <- foos do
>>> > > case barify(foo) do
>>> > > {:ok, bar} -> bar
>>> > > {:error, reason} -> break(reason)
>>> > > end
>>> > > end
>>> > >
>>> > > I think this would have to work similarly to how Ecto's transactions
>>> > > work with Multis, that is return {:ok, bars} or {:error, reason,
>>> > > data_so_far}.
>>> > >
>>> > > I have found only one usage of Enum.reduce_while in Elixir's
>>> > > codebase. Interestingly, the shape of the return value is always
>>> > > the same - a list of finished tests.
>>> > >
>>> https://github.com/elixir-lang/elixir/blob/main/lib/ex_unit/lib/ex_unit/runner.ex#L340
>>> > >
>>> > > This seems like a separate problem, but maybe something to keep in
>>> > > mind.
>>> > >
>>> > > Best,
>>> > > Stefan
>>> > >
>>> > >
>>> > > wt., 21 gru 2021 o 00:21 Ben Wilson <benwil...@gmail.com>
>>> > > napisał(a):
>>> > >
>>> > > > To revisit the example situation from the original post:
>>> > > >
>>> > > > ```
>>> > > > {sections, _acc} =
>>> > > > for let {section_counter, lesson_counter} = {1, 1}, section <-
>>> > > > sections do lesson_counter = if section["reset_lesson_position"],
>>> > > > do: 1, else: lesson_counter
>>> > > > {lessons, lesson_counter} = for let lesson_counter, lesson <-
>>> > > > section["lessons"] do
>>> > > > {Map.put(lesson, "position", lesson_counter), lesson_counter + 1}
>>> > > > end
>>> > > > section =
>>> > > > section
>>> > > > |> Map.put("lessons", lessons)
>>> > > > |> Map.put("position", section_counter)
>>> > > >
>>> > > > {section, {section_counter + 1, lesson_counter}}
>>> > > > end
>>> > > > ```
>>> > > >
>>> > > > I think that's nice! It focuses on inputs and outputs and reduces
>>> > > > the overall line noise.
>>> > > >
>>> > > > On Monday, December 20, 2021 at 5:28:29 PM UTC-5 José Valim wrote:
>>> > > >
>>> > > >> Stefan, this would work if we include all extensions:
>>> > > >>
>>> > > >> for reduce {status, acc} = {:ok, []}, status == :ok, foo <- foos
>>> > > >> do case barify(foo) do
>>> > > >> {:ok, bar} -> {:ok, [bar | acc]}
>>> > > >>
>>> > > >> {:error, _reason} = error -> error
>>> > > >> end
>>> > > >> end
>>> > > >>
>>> > > >> I am not sure if you find it any better. It is hard to do this
>>> > > >> with "let" because you don't want to include the element of when
>>> > > >> it fails.
>>> > > >>
>>> > > >> On Mon, Dec 20, 2021 at 9:23 PM Stefan Chrobot
>>> > > >> <ste...@chrobot.io> wrote:
>>> > > >>> I went through some of our code and one thing I'd love to see is
>>> > > >>> a way to replace Enum.reduce_while with the for comprehension.
>>> > > >>> So the code like this:
>>> > > >>>
>>> > > >>> Enum.reduce_while(foos, {:ok, []}, fn foo, {:ok, bars} ->
>>> > > >>> case barify(foo) do
>>> > > >>> {:ok, bar} -> {:cont, {:ok, [bar | bars]}}
>>> > > >>> {:error, _reason} = error -> {:halt, error}
>>> > > >>> end
>>> > > >>> end)
>>> > > >>>
>>> > > >>> Would the following even work?
>>> > > >>>
>>> > > >>> for reduce(result = {:ok, []}), foo <- foos, {:ok, _} <- result
>>> > > >>> do case barify(foo) do
>>> > > >>> {:ok, bar} -> {{:ok, [bar | bars]}}
>>> > > >>> {:error, _reason} = error -> {error}
>>> > > >>> end
>>> > > >>> end
>>> > > >>>
>>> > > >>> Even if it did, it's not doing a great job of communicating the
>>> > > >>> intent and still potentially requires a Enum.reverse call. The
>>> > > >>> intent here is "early exit with some value upon some condition
>>> > > >>> or pattern mismatch".
>>> > > >>>
>>> > > >>>
>>> > > >>> Best,
>>> > > >>> Stefan
>>> > > >>>
>>> > > >>> pon., 20 gru 2021 o 21:06 Stefan Chrobot <ste...@chrobot.io>
>>> > > >>> napisał(a):
>>> > > >>>> I really like this proposal! For me it strikes the perfect
>>> > > >>>> balance between terseness and explicitness that I've come to
>>> > > >>>> enjoy in Elixir.
>>> > > >>>>
>>> > > >>>> My votes:
>>> > > >>>> - Naming: let over given; just because it's shorter,
>>> > > >>>> - Do use parents: let "feels" similar to var!.
>>> > > >>>>
>>> > > >>>> Best,
>>> > > >>>> Stefan
>>> > > >>>>
>>> > > >>>> pon., 20 gru 2021 o 19:54 José Valim <jose....@dashbit.co>
>>> > > >>>> napisał(a):
>>> > > >>>>> Good point. I forgot to mention the :reduce option will be
>>> > > >>>>> deprecated in the long term.
>>> > > >>>>>
>>> > > >>>>> On Mon, Dec 20, 2021 at 7:53 PM 'eksperimental' via
>>> > > >>>>> elixir-lang-core < elixir-l...@googlegroups.com> wrote:
>>> > > >>>>>
>>> > > >>>>>> The proposal is very concise,
>>> > > >>>>>> the only thing that would be problematic is the use of
>>> > > >>>>>> `reduce` for two
>>> > > >>>>>> different things,
>>> > > >>>>>>
>>> > > >>>>>> for <<x <- "AbCabCABc">>, x in ?a..?z, reduce: %{} do
>>> > > >>>>>> acc -> Map.update(acc, <<x>>, 1, & &1 + 1)
>>> > > >>>>>> end
>>> > > >>>>>>
>>> > > >>>>>> {sum, count} =
>>> > > >>>>>> for reduce({sum, count} = {0, 0}), i <- [1, 2, 3] do
>>> > > >>>>>> sum = sum + i
>>> > > >>>>>> count = count + 1
>>> > > >>>>>> {sum, count}
>>> > > >>>>>> end
>>> > > >>>>>>
>>> > > >>>>>> It would lead to misunderstanding as it may not be clear
>>> > > >>>>>> which one we are talking about when we say "use for reduce"
>>> > > >>>>>>
>>> > > >>>>>>
>>> > > >>>>>> On Mon, 20 Dec 2021 19:11:54 +0100
>>> > > >>>>>> José Valim <jose....@dashbit.co> wrote:
>>> > > >>>>>>
>>> > > >>>>>> > Hi everyone,
>>> > > >>>>>> >
>>> > > >>>>>> > This is the second proposal for-let. You can find it in a
>>> > > >>>>>> > gist:
>>> > > >>>>>> >
>>> https://gist.github.com/josevalim/fe6b0bcc728539a5adf9b2821bd4a0f5
>>> > > >>>>>> >
>>> > > >>>>>> > Please use the mailing list for comments and further
>>> > > >>>>>> > discussion. Thanks for all the feedback so far!
>>> > > >>>>>> >
>>> > > >>>>>>
>>> > > >>>>>> --
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>>> > > >>>>>> .
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>>> > > >>>>> <
>>> https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4LOyoAmXULJQo%2BYX4eFVJZJAoYtKHytoHujCS_kJ6AEuA%40mail.gmail.com?utm_medium=email&utm_source=footer
>>> >
>>> > > >>>>> .
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>>> > > >>> <
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>>> >
>>> > > >>> .
>>> > > >>>
>>> > > >> --
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>>> > > > <
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>>> >
>>> > > > .
>>> > > >
>>> > >
>>> >
>>>
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