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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