I've made a PR here, but I'm happy to change change the name if we land on something better: https://github.com/elixir-lang/elixir/pull/10532/files
I personally still prefer `count_until`. On Friday, December 4, 2020 at 11:24:06 AM UTC-5 ad...@a-corp.co.uk wrote: > What about count_upto or count_up_to > > This is similar to the ruby method .upto. > > > > On Fri, 4 Dec 2020 at 16:20, Zachary Daniel <zachary....@gmail.com> wrote: > >> `count_while` would imply (to me) that it counts while a predicate >> returns true. The only name I can think of that would be expressive and >> consistent with other Enum functions would be something like >> `Enum.count_take` or `Enum.take_count`, but I think that `Enum.take_until` >> is a better name. >> >> On Friday, December 4, 2020 at 10:50:18 AM UTC-5 mario.luis...@gmail.com >> wrote: >> >>> This would be the first function in Enum with "until" in its name. For >>> consistency with the other functions in this module, wouldn't it be >>> preferable the "while" suffix instead ? >>> >>> A sexta-feira, 4 de dezembro de 2020 à(s) 07:29:29 UTC, José Valim >>> escreveu: >>> >>>> We can also add Enum.count_until(enumerable, filter, n) and you can use >>>> filter = & &1 if you want to force enumeration, like there is for >>>> Enum.count/2 today. >>>> >>>> On Fri, Dec 4, 2020 at 8:28 AM José Valim <jose....@dashbit.co> wrote: >>>> >>>>> That's a very good point Jayson. I think we should go with "count >>>>> until should take advantage of all optimizations and ignore >>>>> side-effects”. >>>>> I believe it is fair to expect that no enumerable that implements count >>>>> actually has side-effects, exactly because of the implications of what >>>>> you >>>>> said. >>>>> >>>>> On Fri, Dec 4, 2020 at 8:08 AM 'Jayson Vantuyl' via elixir-lang-core < >>>>> elixir-l...@googlegroups.com> wrote: >>>>> >>>>>> There are three questions I don’t think we’re considering: >>>>>> * What does it mean to “partially count” an Enumerable that >>>>>> implements an “efficient” `count/1` function? >>>>>> * If such an Enumerable has side-effects for its `reduce/3` function, >>>>>> should they be somehow still happen even though the `count/1` doesn’t >>>>>> necessarily iterate the elements? >>>>>> * If such an Enumerable returns a larger count that asked for, should >>>>>> we return the larger “technically correct” value; or the `max + 1` value? >>>>>> >>>>>> I generally like `count_until/2` because it‘s unopinionated about >>>>>> what you’re doing with the count. But the answers to the above question >>>>>> probably should be addressed and documented. >>>>>> >>>>>> I really see two ways to address the above question. Either we >>>>>> consider “count until implies actively counting” or “count until should >>>>>> take advantage of all optimizations and ignore side-effects”. >>>>>> >>>>>> My feel is that the latter is generally going to be more efficient in >>>>>> the common case but the former is less likely to create unexpected >>>>>> behavior >>>>>> from people who don’t know how their Enumerable is implemented. >>>>>> >>>>>> I’m inclined to favor the former. It won’t throw away efficiency that >>>>>> a custom Enumerable will implement, it’ll generally make naive code >>>>>> faster, >>>>>> and the rare cases where people expect side-effects is probably less >>>>>> important than either of those other benefits. >>>>>> >>>>>> Sent from my iPhone >>>>>> >>>>>> On Dec 3, 2020, at 21:18, José Valim <jose....@dashbit.co> wrote: >>>>>> >>>>>> >>>>>> Thanks Allen! I believe that's a good idea. >>>>>> >>>>>> I think the main insight is that we don't want a predicate function >>>>>> (at_least? more_than?). Using compare returns three states - which is >>>>>> better than two - but what if we just returned the number? After all, if >>>>>> I >>>>>> am interested in knowing if something has less than 10, 10, or more than >>>>>> 10, I just need to count until eleven. Returning a number seems to be >>>>>> more >>>>>> flexible too. Therefore, what do you think about: count_until(enum, >>>>>> value)? >>>>>> >>>>>> To check if less, eq, or more than 10: >>>>>> >>>>>> case Enum.count_until(count, 10 + 1) do >>>>>> 11 -> :gt >>>>>> 10 -> :eq >>>>>> _ -> :lt >>>>>> end >>>>>> >>>>>> For at least 10: >>>>>> >>>>>> Enum.count_until(count, 10) == 10 >>>>>> >>>>>> For more than 10: >>>>>> >>>>>> Enum.count_until(count, 10 + 1) > 10 >>>>>> >>>>>> Thoughts? >>>>>> >>>>>> >>>>>> On Fri, Dec 4, 2020 at 2:14 AM Zach Daniel <zachary....@gmail.com> >>>>>> wrote: >>>>>> >>>>>>> Yep! I really like it :) >>>>>>> >>>>>>> On Thu, Dec 3, 2020 at 7:52 PM eksperimental < >>>>>>> eksper...@autistici.org> wrote: >>>>>>> >>>>>>>> On Thu, 3 Dec 2020 19:06:18 -0500 >>>>>>>> Allen Madsen <allen.c...@gmail.com> wrote: >>>>>>>> >>>>>>>> > Enum.compare_count([], 1) #=> :lt >>>>>>>> > Enum.compare_count([1], 1) #=> :eq >>>>>>>> > Enum.compare_count([1, 2], 1) #=> :gt >>>>>>>> >>>>>>>> This is the way to go, because in one function call we can >>>>>>>> determine the >>>>>>>> course of the action, such as in >>>>>>>> >>>>>>>> case Enum.compare_count(list, n) do >>>>>>>> :lt -> ... >>>>>>>> :eq -> ... >>>>>>>> :gt -> ... >>>>>>>> end >>>>>>>> >>>>>>>> when using the predicate functions it would require at least two >>>>>>>> function calls. >>>>>>>> >>>>>>>> > >>>>>>>> > Allen Madsen >>>>>>>> > http://www.allenmadsen.com >>>>>>>> > >>>>>>>> > >>>>>>>> > On Thu, Dec 3, 2020 at 6:51 PM Zach Daniel >>>>>>>> > <zachary....@gmail.com> wrote: >>>>>>>> > >>>>>>>> > > Well, List.count doesn’t exist yet, but either way it sounds >>>>>>>> like >>>>>>>> > > not a great idea :) I couldn’t find examples in other Lang’s, so >>>>>>>> > > maybe I’ll just throw out some other names: >>>>>>>> > > >>>>>>>> > > Enum.at_least?/2 >>>>>>>> > > >>>>>>>> > > Enum.at_most?/2 >>>>>>>> > > >>>>>>>> > > Enum.has_count?/2 >>>>>>>> > > >>>>>>>> > > On Thu, Dec 3, 2020 at 5:14 PM Michał Muskała < >>>>>>>> mic...@muskala.eu> >>>>>>>> > > wrote: >>>>>>>> > > >>>>>>>> > >> Unfortunately this can’t be done automatically since it has >>>>>>>> subtle >>>>>>>> > >> semantic differences. In particular Enum.count/1 (or length/1) >>>>>>>> not >>>>>>>> > >> only traverses the list to count its size, but also verifies >>>>>>>> it’s >>>>>>>> > >> a proper list raising an exception for improper lists. The >>>>>>>> > >> difference could be seen for value like: >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> [1, 2, 3 | :invalid] >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> Calling length/1 or Enum.count/1 on this raises. If compiler >>>>>>>> did >>>>>>>> > >> the optimisation you propose, for something like length(list) >>>>>>>> > 0, >>>>>>>> > >> it wouldn’t fully traverse the list and wouldn’t raise. Thus >>>>>>>> such >>>>>>>> > >> an optimisation is not possible in the general case. >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> *From: *elixir-l...@googlegroups.com < >>>>>>>> > >> elixir-l...@googlegroups.com> >>>>>>>> > >> *Date: *Thursday, 3 December 2020 at 22:04 >>>>>>>> > >> *To: *elixir-l...@googlegroups.com < >>>>>>>> > >> elixir-l...@googlegroups.com> >>>>>>>> > >> *Subject: *Re: [elixir-core:9802] Proposal `Enum.more_than?/2` >>>>>>>> or >>>>>>>> > >> `List.more_than?/2` >>>>>>>> > >> >>>>>>>> > >> This probably off the table/unreasonable, but it also seems >>>>>>>> like >>>>>>>> > >> something that could be statically solved and people would >>>>>>>> never >>>>>>>> > >> need to know as it is just an optimization. E.g >>>>>>>> Enum.count(list) > >>>>>>>> > >> n could optimized by the compiler? Probably wouldn’t be good >>>>>>>> for >>>>>>>> > >> all Enums, since counting would be expected to enumerate them, >>>>>>>> so >>>>>>>> > >> maybe only something like List.count 🤷♂️ >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> On Thu, Dec 3, 2020 at 1:42 PM Zach Daniel >>>>>>>> > >> <zachary....@gmail.com> wrote: >>>>>>>> > >> >>>>>>>> > >> Another benefit to the options list would be supporting it for >>>>>>>> > >> count with a predicate, e.g Enum.count(enum, &some_predicate/1, >>>>>>>> > >> max: 4) >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> On Thu, Dec 3, 2020 at 1:35 PM Zach Daniel >>>>>>>> > >> <zachary....@gmail.com> wrote: >>>>>>>> > >> >>>>>>>> > >> Nothing is jumping out at me from elsewhere yet, but another >>>>>>>> > >> option might be accepting options in `Enum.count`, like >>>>>>>> > >> `Enum.count(list, max: 4)`. I’ll keep searching though. >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> On Thu, Dec 3, 2020 at 1:31 PM Zach Daniel >>>>>>>> > >> <zachary....@gmail.com> wrote: >>>>>>>> > >> >>>>>>>> > >> I agree on the name feeling subpar :) I’ll take a look and see >>>>>>>> if >>>>>>>> > >> I can find other examples. >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> On Thu, Dec 3, 2020 at 12:21 PM José Valim < >>>>>>>> jose....@dashbit.co> >>>>>>>> > >> wrote: >>>>>>>> > >> >>>>>>>> > >> Thanks Zach! I like this idea but the proposed name, for some >>>>>>>> > >> reason, doesn't sit right with me. Is there any prior art from >>>>>>>> > >> other langs we could look at? >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> On Thu, Dec 3, 2020 at 6:15 PM Zachary Daniel >>>>>>>> > >> <zachary....@gmail.com> wrote: >>>>>>>> > >> >>>>>>>> > >> Counting a list, especially a large one, to know if there are >>>>>>>> > >> "more than x" or "less than x" items is inefficient. >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> Right now I often see things like `if Enum.count(list) > 4 >>>>>>>> ...`, >>>>>>>> > >> mostly because writing a recursive `more_than?` check is >>>>>>>> tedious, >>>>>>>> > >> or doing something like `Enum.empty?(Enum.drop(list, 4))` is >>>>>>>> not >>>>>>>> > >> very expressive. >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> >>>>>>>> > >> I think it would be nice to have an `Enum.more_than?` that does >>>>>>>> > >> that work for you. It could also be `List.more_than?/2` if we >>>>>>>> > >> don't want it in Enum. Any thoughts? >>>>>>>> > >> >>>>>>>> > >> -- >>>>>>>> > >> 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/263d7c39-a32b-4294-93d8-40f248c9b3c8n%40googlegroups.com >>>>>>>> > >> < >>>>>>>> https://groups.google.com/d/msgid/elixir-lang-core/263d7c39-a32b-4294-93d8-40f248c9b3c8n%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-co...@googlegroups.com. >>>>>>>> > >> To view this discussion on the web visit >>>>>>>> > >> >>>>>>>> https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4JX4NE1yWH1G5L_DjF18v8zejF0%2BSkb_oz%3DPiUHM8Mz1w%40mail.gmail.com >>>>>>>> > >> < >>>>>>>> https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4JX4NE1yWH1G5L_DjF18v8zejF0%2BSkb_oz%3DPiUHM8Mz1w%40mail.gmail.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-co...@googlegroups.com. >>>>>>>> > >> >>>>>>>> > >> To view this discussion on the web visit >>>>>>>> > >> >>>>>>>> https://groups.google.com/d/msgid/elixir-lang-core/CAK-yb0BBGCrgbZamFs%2BeqLUis6mFQgvUHkKK1htSN5rDDWwMRQ%40mail.gmail.com >>>>>>>> > >> < >>>>>>>> https://groups.google.com/d/msgid/elixir-lang-core/CAK-yb0BBGCrgbZamFs%2BeqLUis6mFQgvUHkKK1htSN5rDDWwMRQ%40mail.gmail.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-co...@googlegroups.com. >>>>>>>> > >> To view this discussion on the web visit >>>>>>>> > >> >>>>>>>> https://groups.google.com/d/msgid/elixir-lang-core/DB7PR07MB3899C92933992464F17898E1FAF20%40DB7PR07MB3899.eurprd07.prod.outlook.com >>>>>>>> > >> < >>>>>>>> https://groups.google.com/d/msgid/elixir-lang-core/DB7PR07MB3899C92933992464F17898E1FAF20%40DB7PR07MB3899.eurprd07.prod.outlook.com?utm_medium=email&utm_source=footer >>>>>>>> > >>>>>>>> > >> . >>>>>>>> > >> >>>>>>>> > > -- >>>>>>>> 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