Even the "map_reduce: ..." option I proposed a couple times, and it was not
accepted, can be implemented today, although it is quite more verbose than
simply piping the result:
# double each element and compute the sum at once
{mapped, reduce} =
for x <- collection, reduce: {[], 0} do
{list, acc} -> {[x * 2 | list], acc + x}
end
{Enum.reverse(mapped), reduce}
*José Valimhttps://dashbit.co/ <https://dashbit.co/>*
On Sat, Nov 16, 2024 at 11:28 AM José Valim <jose.va...@gmail.com> wrote:
> It does conflict in the same way. What does this mean: "into: %{},
> reverse: true"? Or "into: <<>>, reverse: true"? Do you reverse bytes or
> graphemes? "reduce: ..., reverse: true" also only works if you reduce into
> a list, which is rarely the case.
>
> The key aspect to keep in mind is that "into: ..." already gives options
> to do all of this. You could have a "ReverseList" collectable, a "Joiner"
> collectable, or "ReverseBytes".
>
> And "for" is already complex enough, I don't think we should add options
> such as `then: ...` which is syntax sugar to an already existing construct.
>
> As far as I know, the constructs you cannot do today using either into or
> reduce is zipping, or anything that aborts early (reduce_while or
> take/drop), which would be a break in other programming languages.
>
>
> *José Valimhttps://dashbit.co/ <https://dashbit.co/>*
>
>
> On Sat, Nov 16, 2024 at 10:59 AM Daniel Kukula <daniel.k...@gmail.com>
> wrote:
>
>> I have also one proposal to for loops:
>> reverse: true
>> for applies already the reverse and when I don't care about the order, or
>> want to reverse the result anyway then it has to be reversed twice.
>> It would be a nice addition that could add a small bit of performance in
>> some cases. Also it should not conflict with existing features?.
>>
>> On Friday, November 15, 2024 at 3:16:04 PM UTC+1 cbla...@gmail.com wrote:
>>
>>> What I'm proposing, is only syntaxic sugar.
>>>
>>> I don't like piping comprehension's result. It looks less readable than
>>> piping with regular Enum functions.
>>> Le 15 nov. 2024 à 12:42 +0100, José Valim <jose....@gmail.com>, a écrit
>>> :
>>>
>>> But then why not simply pipe to the result afterwards? This is all
>>> possible today already:
>>>
>>> for(...) |> Enum.join(", ")
>>> for(...) |> then(&Enum.join(&1, ", "))
>>>
>>> for do
>>> ...
>>> end |> then(&Enum.join(&1, ", "))
>>>
>>>
>>> *José Valim*
>>> https://dashbit.co/
>>>
>>>
>>> On Fri, Nov 15, 2024 at 11:13 AM Christian Blavier <cbla...@gmail.com>
>>> wrote:
>>>
>>>> My point wasn’t about adding a join but a then option (like
>>>> Kernel.then), which seems much more versatile.
>>>>
>>>> Whatever I was expecting a no :)
>>>> Le 15 nov. 2024 à 11:10 +0100, José Valim <jose....@gmail.com>, a
>>>> écrit :
>>>>
>>>> It is the same answer as before, I am afraid. The path to adding :join
>>>> is also the path to adding :intersperse, and :sum, and :product, etc. We
>>>> should have a general mechanism for expressing those, instead of individual
>>>> options.
>>>>
>>>> And, as before, a joiner does not really work well with into and reduce.
>>>>
>>>>
>>>> *José Valim*
>>>> https://dashbit.co/
>>>>
>>>>
>>>> On Fri, Nov 15, 2024 at 11:06 AM Christian Blavier <cbla...@gmail.com>
>>>> wrote:
>>>>
>>>>> Hey there,
>>>>>
>>>>> I'm still thinking about extending comprehension. What about a `then`
>>>>> option?
>>>>>
>>>>> for i <- 1..3, do: i, then: &Enum.sum/1
>>>>>
>>>>> for s <- ~w(a b c), do: s, then: &Enum.join(&1, ", ")
>>>>>
>>>>> (I know this can be achieved more efficiently with a reduce, but
>>>>> sometimes concise syntax is a better choice)
>>>>>
>>>>> Le mardi 21 juin 2022 à 18:40:46 UTC+2, José Valim a écrit :
>>>>>
>>>>>> It should probably be done with using `into: joiner(",")`, where the
>>>>>> joiner implements the collectable protocol. join itself probably doesn't
>>>>>> make much sense because it doesn't play well with other options such as
>>>>>> :into itself, or :reduce.
>>>>>>
>>>>>> On Tue, Jun 21, 2022 at 6:15 PM Christian Blavier <cbla...@gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Do you think a join option would be a good idea for comprehensions?
>>>>>>> Something like Enum.map_join/2 that could map and join lists in a
>>>>>>> single pass.
>>>>>>> book_ids = for book <- books, join: ",", do: book.id
>>>>>>>
>>>>>>> If it looks like a good idea, I will open a PR.
>>>>>>>
>>>>>>> Best,
>>>>>>>
>>>>>>> Christian
>>>>>>>
>>>>>>> --
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