Thanks for the proposal. The issue with contains? is that it is slightly ambiguous in that it is unclear if List.contains?(list, [1, 2]) is meant to be positive for [[1, 2]] or [1, 2]. In Strings there is no such ambiguity. So I would personally avoid contains? in favor of something clearer. Therefore I would love to see if other languages have this function and what they call it. :)
Regarding the implementation, I also think one of the several string lookup techniques could be used here. The recursive approach is better but it has O(m*n) worst case complexity. The "bad character rule" from Boyer–Moore <https://en.wikipedia.org/wiki/Boyer%E2%80%93Moore_string_search_algorithm> shouldn't add too much complexity and can provide a meaningful improvement. On Fri, Jul 15, 2022 at 3:32 PM Julian Somoza <julian.som...@gmail.com> wrote: > Thanks for your replies, > > yes, it could be an String.contains? analog: > > [1,2,"3",4] |> Enum.join |> String.contains?("34") > [1,:a,"3",4] |> Enum.join |> String.contains?("a3") > > About the recursive version, it seems to have best performance: > > [image: image.png] > > [image: image.png] > > El vie, 15 jul 2022 a las 9:38, Aleksei Matiushkin (< > aleksei.matiush...@kantox.com>) escribió: > >> I have not benchmarked it, but I believe the recursive approach would be >> better >> >> ``` >> defmodule MyList do >> def contains?(list, sublist, strict? \\ false) >> >> def contains?(_, [], _), do: true >> def contains?([], _, _), do: false >> def contains?([h | t], [hh | _] = sub, strict?) when h != hh, do: not >> strict? and contains?(t, sub, strict?) >> def contains?([h | t], [h | tt], strict?), do: contains?(t, tt, true) >> or contains?(t, [h | tt], strict?) >> end >> ``` >> >> On Fri, Jul 15, 2022 at 2:07 PM 'eksperimental' via elixir-lang-core < >> elixir-lang-core@googlegroups.com> wrote: >> >>> Hi Julian. >>> It think it is a good addition. >>> It is also analog to String.contains?/2 >>> >>> On Fri, 15 Jul 2022 04:58:59 -0700 (PDT) >>> Julian Somoza < >>> https://urldefense.proofpoint.com/v2/url?u=http-3A__julian.somoza-40gmail.com&d=DwICaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=rmhwzhuTk1LyLPLZIrqkat6wS6r2qE3XZKnTTHGaxH8&m=rZfYwgMRyMdd1mpKac91VLHbd0qUJlcEVeNzbceWXvE&s=T8KKoaIf0UYlrJ_VQC1Qv_48Tje2jygIaQysVTXu2c0&e=> >>> wrote: >>> >>> > Hi everyone, I was working on a suggestion to add a new function on >>> > the List module in order to find out if a given sublist is inside >>> > another list. >>> > >>> > We currently have *List.starts_with?/2* but this only match the >>> > beginning: >>> > >>> > iex(1)> List.starts_with?([1, 2, 3], [1, 2]) >>> > true >>> > >>> > Besides, we have *MapSet.subset*, but it ignores the elements order: >>> > >>> > iex(1)> MapSet.subset?(MapSet.new([1, 2]), MapSet.new([1, 2, 3])) >>> > true >>> > >>> > iex(1)> MapSet.subset?(MapSet.new([2, 1]), MapSet.new([1, 2, 3])) >>> > true >>> > >>> > I suggest a new function that works like *List.starts_with?/2* but >>> > matches the entire list, either at the beginning, middle, or end of >>> > the list. >>> > >>> > iex(1)> List.includes_sublist?([1,2,3,4,5], [2,3]) >>> > true >>> > >>> > iex(1)> List.includes_sublist?([1,2,3,4,5], [1,2]) >>> > true >>> > >>> > iex(1)> List.includes_sublist?([1,2,3,4,5], [3,4,5]) >>> > true >>> > >>> > iex(1)> List2.includes_sublist?([1,2,3,4,5], [1,5]) >>> > false >>> > >>> > I'm sharing with you also the function code: >>> > >>> > >>> https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_elixir-2Dlang_elixir_pull_11987_commits_2b7eba5f6419f906f565e7d4bfe3d687f3b8b052&d=DwICaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=rmhwzhuTk1LyLPLZIrqkat6wS6r2qE3XZKnTTHGaxH8&m=rZfYwgMRyMdd1mpKac91VLHbd0qUJlcEVeNzbceWXvE&s=rqpOP9kyNDkOSBV-I2zlHssI6EVLQQ-iBW1F0k3nqFg&e= >>> > >>> > I aim to complement the List.starts_with?/2. This function could be >>> > the same or even more useful because it finds the ordered sublist >>> > also in the middle or in the end. >>> > >>> > Looking forward for your comments, >>> > BR, >>> > Julian Somoza. >>> > >>> > >>> >>> -- >>> 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://urldefense.proofpoint.com/v2/url?u=https-3A__groups.google.com_d_msgid_elixir-2Dlang-2Dcore_62d1588e.1c69fb81.3332c.1d2dSMTPIN-5FADDED-5FMISSING-2540gmr-2Dmx.google.com&d=DwICaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=rmhwzhuTk1LyLPLZIrqkat6wS6r2qE3XZKnTTHGaxH8&m=rZfYwgMRyMdd1mpKac91VLHbd0qUJlcEVeNzbceWXvE&s=Ckh5t8xdml-Vx3UgfKMNxh3CoSb8IBfBORyYgVxcXsg&e= >>> . >>> >> >> >> -- >> *Aleksei Matiushkin*, Software Engineer - R&D >> >> Office (+34) 935 679 834 >> >> >> >> 8 Devonshire Square, London, EC2M 4PL, United Kingdom >> Torre Mapfre, Planta 22, Marina, 16-18, 08005 Barcelona, Spain >> *kantox.com <http://kantox.com/>* >> >> >> >> >> >> >> >> >> >> >> <http://www.linkedin.com/company/1871617> >> <http://www.linkedin.com/company/1871617>[image: LinkedIn] >> <https://www.linkedin.com/company/1871617> >> <https://twitter.com/kantox>[image: Twitter] <https://twitter.com/kantox> >> <http://www.youtube.com/user/kantoxfx>[image: YouTube] >> <https://www.youtube.com/user/kantoxfx> >> >> Kantox Limited is a UK private company with registered company number >> 07657495 and registered address at 8 Devonshire Square, London EC2M 4PL, >> United Kingdom. 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