I'm in a similar situation to you YongHao. Sorry, but would you mind if I
did it?
To be clear the functionality would be:
DateTime.earliest(enumerable, mapper \\ fn x -> x end)
with a typespec like
@spec earliest(Enum.t(), (any() -> t())) :: list()
right?
On Thursday, October 10, 2019 at 4:42:45 PM UTC+8, YongHao Hu wrote:
>
> If Tyson Buzza don't mind, I would love to write this as my first PR as I
> had used Elixir in work for two years and want to do a contribution. : P
>
> On Thu, Oct 10, 2019 at 4:29 PM José Valim <jose...@plataformatec.com.br
> <javascript:>> wrote:
>
>> Oh, I see why you called it sort_earliest, because you also want to allow
>> a function to be given, in the style of sort_by. I am not a big fan of
>> sort_earliest though.
>>
>> What if we add only: DateTime.earliest(list_of_dates) and
>> DateTime.earliest(list_of_dates, fun)? You can always get the earliest of
>> two dates by passing it a list with two elements.
>>
>>
>> *José Valim*
>> www.plataformatec.com.br
>> Skype: jv.ptec
>> Founder and Director of R&D
>>
>>
>> On Thu, Oct 10, 2019 at 5:26 AM José Valim <jose...@plataformatec.com.br
>> <javascript:>> wrote:
>>
>>> I love this. My suggestion is to add earliest(date, date) and
>>> earliest(list_of_dates) and the same for latest. We need to add it to Time,
>>> Date, NaiveDateTime and DateTime.
>>>
>>> A PR is very appreciated.
>>>
>>>
>>> *José Valim*
>>> www.plataformatec.com.br
>>> Skype: jv.ptec
>>> Founder and Director of R&D
>>>
>>>
>>> On Thu, Oct 10, 2019 at 5:15 AM Tyson Buzza <tyson...@gmail.com
>>> <javascript:>> wrote:
>>>
>>>> I have been using DateTime and NaiveDateTime alot over the last year
>>>> and have found that using the compare function to involves some mental
>>>> gymnastics. When using compare you often just want the most recent or
>>>> oldest timestamp, or else you want to sort a list of timestamps.
>>>>
>>>> I am proposing four new functions for each module: earliest/2,
>>>> latest/2, sort_earliest/2, and sort_latest/2. earliest/2 and latest/2
>>>> each
>>>> take two DateTime structs and return the first/last time respectively. The
>>>> sort_earliest/2 and sort_latest/2 functions take a list and an optional
>>>> mapper, similar to the Enum.sort_by/2 function. sort_earliest/2 and
>>>> sort_latest/2 will return the list in ascending/descending chronological
>>>> order respectively.
>>>>
>>>> Example usage:
>>>>
>>>> ```
>>>> start_time = DateTime.earliest(datetime1, datetime2)
>>>> start_time = Enum.reduce(datetime_list, &DateTime.earliest/2)
>>>> sorted_times = DateTime.sort_earliest(datetime_list)
>>>> sorted_records = DateTime.sort_earliest(records, &(&1.timestamp))
>>>> ```
>>>>
>>>> This example is a function that uses sort_earliest to check if a time
>>>> is inside a given time range:
>>>>
>>>> ```
>>>> def in_range(time_stamp, {start_time, end_time} = _range) do
>>>> case sort_earliest([time_stamp, start_time, end_time]) do
>>>> [^start_time, ^time_stamp, ^end_time] ->
>>>> true
>>>>
>>>> _ ->
>>>> false
>>>> end
>>>> end
>>>> ```
>>>>
>>>> The implementation would be something simple like this:
>>>>
>>>> ```
>>>> def sort_earliest(list, mapper \\ fn x -> x end) do
>>>> Enum.sort_by(list, mapper, fn x, y ->
>>>> :lt == DateTime.compare(x, y)
>>>> end)
>>>> end
>>>>
>>>> def earliest(%DateTime{} = datetime1, %DateTime{} = datetime2) do
>>>> case DateTime.compare(datetime1, datetime2) do
>>>> :gt ->
>>>> datetime2
>>>>
>>>> _ ->
>>>> datetime1
>>>> end
>>>> end
>>>> ```
>>>>
>>>> Might need to make sure sort_earliest is an in place sort.
>>>>
>>>> --
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>>>>
>>>> <https://groups.google.com/d/msgid/elixir-lang-core/47178019-74cd-44bd-b26e-4b092c5c04a2%40googlegroups.com?utm_medium=email&utm_source=footer>
>>>> .
>>>>
>>> --
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>>
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>> .
>>
>
>
> --
> --
> Regards,
> YongHao Hu
>
>
>
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