Please compare
coll |> Enum.map_reverse(&my_fun/1)
to
coll |> Enum.reduce([], fn ele, acc -> [fun(ele)|acc] end)
And also would Enum.map_reverse/2 not be even more optimized, although
performance was not my primary motivation.
--
Non datemi consigli che so sbagliare da solo
(Giuseppe Di Stefano)
On Sun, Mar 31, 2019 at 6:01 PM Andrea Leopardi <[email protected]>
wrote:
> You can do the same in an efficient way with Enum.reduce/3 and prepending
> to the accumulator:
>
> Enum.reduce(list, [], fn elem, acc ->
> [fun.(elem) | acc ]
> end)
>
> I think given this is small and straightforward, an addition of
> reverse_map to the standard library could be something that we can avoid.
>
> Andrea
>
> On Sun, 31 Mar 2019 at 17:58, Robert Dober <[email protected]> wrote:
>
>> Hi there
>>
>> I do this all the time, travering a reversed list and accumulating a
>> transformation into a new list, unreversed now.
>>
>> Is this not a very frequent FP pattern.
>>
>> I would quite happy to use `Enum.reverse_map` which would be more
>> efficent than my eternal internal remimplementation:
>>
>> ```elixir
>>
>> defp map_reverse(collection, fun)
>> do
>>
>> _map_reverse(collection, fun,
>> [])
>>
>>
>> end
>>
>>
>>
>> defp _map_reverse(collection, fun,
>> result)
>>
>> defp _map_reverse([], _, result)
>> do
>>
>>
>> result
>>
>>
>> end
>>
>> defp _map_reverse([head|rest], fun, result)
>> do
>>
>> _map_reverse(rest, fun,
>> [fun.(head)|result])
>>
>> end
>> ```
>>
>> Any thoughts?
>>
>> KR
>> Robert
>>
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> --
>
> Andrea Leopardi
> [email protected]
>
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