Hmm. I can't give too much detail, but the basic context is a LiveView form where the user selects some ports and the form provides suggestions as they type. Eg, if they type `2` it will suggest `22 - SSH`, `25 - SMTP`, etc.
The currently-selected ports are a list of integers. If `22` is already selected, the LiveView won't suggest it. So if the LiveView gets a message to deselect `22`, it tries to pop it out of the `selections` list. If the pop succeeds, the `suggestions` list can be updated to include port `22` again. If the pop doesn't succeed, we can ignore the message; we can't deselect a port that wasn't selected to start with. I can't combine `selected` and `suggested` (eg by flagging the suggestions which are also selected) because both collections can contain elements that the other doesn't contain; the user may select ports that are not in the suggestions list. And it's not practical to have a top-level list of every possible port and flag each as `selected`, `suggested`, or both, because there are are 65,535 possible ports. So the core of my use case is: I get a user message to remove an item from a list, and after attempting to remove it, I want to take a follow-up action only if the item was was actually in the list. On Friday, March 4, 2022 at 11:05:35 AM UTC-5 José Valim wrote: > Hi Nathan, thanks for the email. Can you please show some examples of > where they could be handy with some context around them? Thank you! > > On Fri, Mar 4, 2022 at 3:45 PM h...@nathanmlong.com <h...@nathanmlong.com> > wrote: > >> This is a modified version of what I proposed in >> https://github.com/elixir-lang/elixir/pull/11681 >> >> Similar to `Map.pop/2` and and `Keyword.pop/2`, I propose adding >> `List.pop/2`. >> >> I also propose adding `List.find_and_pop/2`, which is more generalized >> since it takes a function. >> >> Here are possible implementations. >> >> ```elixir >> @doc """ >> Returns and removes the first value matching `item` in the `list`. >> >> ## Examples >> iex> List.pop([1, 2, 2, 3], 2) >> {2, [1, 2, 3]} >> iex> List.pop([1, 2, 3, 4], 20) >> {nil, [1, 2, 3, 4]} >> """ >> def pop(list, item) do >> find_and_pop(list, &(&1 == item)) >> end >> >> @doc """ >> Returns and removes the first value matching `fun` in the `list`. >> >> ## Examples >> iex> List.find_and_pop([1, 2, 3, 4], &(&1 > 2)) >> {3, [1, 2, 4]} >> iex> List.find_and_pop([1, 2, 3, 4], &(&1 > 20)) >> {nil, [1, 2, 3, 4]} >> """ >> def find_and_pop(list, fun) do >> case Enum.find_index(list, fun) do >> nil -> {nil, list} >> i -> pop_at(list, i) >> end >> end >> ``` >> >> -- >> You received this message because you are subscribed to the Google Groups >> "elixir-lang-core" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to elixir-lang-co...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/elixir-lang-core/bdc98b8c-fc73-40d7-8287-eb0b5d3ea97en%40googlegroups.com >> >> <https://groups.google.com/d/msgid/elixir-lang-core/bdc98b8c-fc73-40d7-8287-eb0b5d3ea97en%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. To unsubscribe from this group and stop receiving emails from it, send an email to elixir-lang-core+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/elixir-lang-core/57bc38e4-2596-415c-8dbf-a235330d459an%40googlegroups.com.
