I love lazy_ too. We use _with for Enum functions such as split_with, but in
Map I prefer lazy_ too now that you brought it up!
> On 12 Dec 2021, at 09:44, José Valim <jose.va...@dashbit.co> wrote:
>
>
> Thank you for the proposal!
>
> I believe we actually discussed this a couple times, but we could never come
> up with a good name. My thoughts as of now:
>
> * The terminology must definitely be "replace", because update is called even
> if the key is nil.
>
> * However, we don't use the "_with" prefix much in the stdlib. However, we do
> have the "_lazy" suffix, which is about invoking a function. So far, the lazy
> suffix is "if such key does not exist, invoke this", but I think it would
> work on "replace_lazy" such as, "invoke this function only if the key exists".
>
> Thoughts?
>
>> On Sun, Dec 12, 2021 at 8:15 AM Andrea Leopardi <an.leopa...@gmail.com>
>> wrote:
>> I really like this and was thinking about this just yesterday, but was
>> struggling to come up with a name. I was thinking of "update_if_existing"
>> but "replace_with" is actually fantastic, follows our conventions, and
>> sounds great. Awesome job!! If others on the core team agree, I think you
>> could send out a PR for this 😊
>>
>>>> On 11 Dec 2021, at 22:24, Mackenzie Morgan <maco...@gmail.com> wrote:
>>>>
>>> Today's Advent of Code puzzle had a handful of us in the Elixir slack
>>> wishing for something that bridged the gap between Map.update/4,
>>> Map.update!/3, and Map.replace/3.
>>>
>>> Map.update/4 litters your map with extra keys you then have to find and
>>> filter out.
>>> Map.update!/3 throws exceptions which can be especially undesirable in a
>>> pipeline.
>>> Map.replace/3 requires you to pre-calculate the new value.
>>>
>>> The goal would be "if this key exists in the map, update its value using
>>> this function."
>>>
>>> I wrote myself a little helper function (below) to wrap Map.replace/3, and
>>> I know someone else said they made a bunch of {key, nil} s and then had to
>>> filter them back out.
>>>
>>> Anyway, Advent of Code probably isn't the only time it'd be helpful to have
>>> that syntactic sugar. Thoughts?
>>>
>>> Mackenzie
>>>
>>> def replace_with(map, key, _) when not is_map_key(map, key), do: map
>>> def replace_with(map, key, f) do
>>> Map.replace(map, key, f.(map[key]))
>>> end
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