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.va...@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-lang-core@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.va...@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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