I'm just now implementing the new callbacks for `ex_cldr_calendars` and in reviewing the implementation for `Calendar.ISO` is strikes me that the whole implementation, except for one line (see below) depends only on other calendar callbacks. And therefore could be moved into the `Calendar` module and used as an implementation for any calendar that implements `Calendar` behaviour.
This line <https://github.com/elixir-lang/elixir/blob/main/lib/elixir/lib/calendar/iso.ex#L1564> would need to change to use `calendar.months_in_year/1` and a few other calls would need to change to be calendar-referenced to. Moving the code might also allow centralising the options handling and exceptions - it's a little unusual for me to see callbacks handling the options validation rather than the public API. I am more than happy to submit a PR for this very small refactor (thanks to the very clean implementation) if this idea is considered to have merit. On Saturday, March 9, 2024 at 1:42:34 AM UTC+11 br...@grox.io wrote: > The biggest question is if we consider the fields in Duration a unit or > not. If they are units, then the most consistent choice is to keep them > singular, to mirror System.time_unit and friends. > > > This is the API I prefer: units. IMHO, it is more important to keep > consistency with Elixir libraries. > > -bt > > On Thu, Mar 7, 2024 at 11:02 PM José Valim <jose....@dashbit.co> wrote: > >> It is worth noting that Date and friends in Elixir require a calendar >> field, which is not present in Duration, and therefore Duration won't be >> usable as Date (and friends). >> >> The biggest question is if we consider the fields in Duration a unit or >> not. If they are units, then the most consistent choice is to keep them >> singular, to mirror System.time_unit and friends. >> >> On Fri, Mar 8, 2024 at 4:55 AM Kip Cole <kipc...@gmail.com> wrote: >> >>> In my head, a Date.t is semantically a duration. So it’s completely >>> valid to pass it as a duration to Date.shift as I see it. Which argues for >>> singular names. >>> >>> This conversation is a bit like “is a date a point in time or an >>> interval”. And the answer is yes, depending. >>> >>> Sent from my iPhone >>> >>> On 8 Mar 2024, at 14:39, Sabiwara Yukichi <sabi...@gmail.com> wrote: >>> >>> >>> I'm personally leaning more towards the plural, because it feels >>> semantically more correct to treat a point of time and a duration as >>> separate. >>> >>> d.year means the same thing if d is either a date or a datetime, but for >>> a duration calling it d.years emphasizes the difference. >>> >>> It could perhaps help catch errors as well, both for the human and the >>> compiler. >>> One (arguably contrived) example would be structurally typed code which >>> doesn't enforce any type in particular but uses the dot access or partial >>> pattern matches like %{year: ..., month: ...} in order to support both >>> dates or datetimes. Passing in a duration wouldn't make sense semantically, >>> having different names would make it fail properly. >>> >>> I also agree with other reasons mentioned, the known standard one >>> especially. >>> >>> Le jeu. 7 mars 2024 à 16:07, 'Theo Fiedler' via elixir-lang-core < >>> elixir-l...@googlegroups.com> a écrit : >>> >>>> Right, it would make using a Duration in combination with the `add/2-3` >>>> functions much harder than it needs to be. So far all time units in Elixir >>>> are singular, and I think we do gain something from consistently sticking >>>> to that, regardless of the context of durations, calendar types and what >>>> not. >>>> >>>> I've seen some libraries allowing both, singular and plural, which i >>>> dont want to have anything to do with, except for mentioning it though >>>> haha. >>>> >>>> What i currently see is: >>>> >>>> Reasons for plural: >>>> - Known standard across various libraries and programming languages >>>> - Sounds natural, to shift a date by "3 months" instead of "3 month". >>>> >>>> Reasons for singular: >>>> - Compatible with time units already defined in Elixir (also relevant >>>> for extending the use of Duration later on) >>>> - Reduced cognitive load as the time units are always spelled the same >>>> regardless of the context >>>> >>>> The reasons for singular do outweigh the reasons for plural, so unless >>>> we're making some very strong points for diverging from that, let's keep >>>> it >>>> singular! >>>> >>>> On Thursday, March 7, 2024 at 7:39:15 AM UTC+1 José Valim wrote: >>>> >>>>> Compatibility with the other time units is an important point. My mind >>>>> is back on singular again. :) >>>>> >>>>> On Thu, Mar 7, 2024 at 07:20 'Theo Fiedler' via elixir-lang-core < >>>>> elixir-l...@googlegroups.com> wrote: >>>>> >>>>>> While i was strongly leaning towards singular, i understand why one >>>>>> would expect plural. Given that seems to be pretty standard in wild, i >>>>>> am >>>>>> fine changing it as well. >>>>>> >>>>>> What mostly put me off about was that we'd end up with `Time.add(t, >>>>>> 3, :minute)` vs `Time.shift(t, minutes: 3)`, which after all, maybe >>>>>> isn't >>>>>> too bad, as we can keep the plural keys exclusive to durations. Another >>>>>> reason for going with plurals is that it _should_ make migrating from >>>>>> some >>>>>> libraries to the standard library relatively straight forward (with the >>>>>> exception of microseconds). >>>>>> >>>>>> On Wednesday, March 6, 2024 at 11:07:52 PM UTC+1 José Valim wrote: >>>>>> >>>>>>> After a quick glance on other programming languages, it seems >>>>>>> Python, Java, Rust, and C# all have plural names. Erlang also uses >>>>>>> plural >>>>>>> in its helper functions in the timer module. So we might want to follow >>>>>>> suit. >>>>>>> >>>>>>> On Wed, Mar 6, 2024 at 23:03 José Valim <jose....@dashbit.co> wrote: >>>>>>> >>>>>>>> We discussed plural vs singular and settled on singular so it >>>>>>>> mirrors the calendar types. Thoughts? >>>>>>>> >>>>>>>> On Wed, Mar 6, 2024 at 23:01 Panagiotis Nezis <pne...@gmail.com> >>>>>>>> wrote: >>>>>>>> >>>>>>>>> +1 for this, awesome work Theo. Shifting dates/timestamps is such >>>>>>>>> a common operation and a standard implementation would be beneficial >>>>>>>>> for >>>>>>>>> everybody. >>>>>>>>> >>>>>>>>> PS. I would expect plural in the duration fields. >>>>>>>>> >>>>>>>>> On Wed, Mar 6, 2024 at 8:23 PM José Valim <jose....@dashbit.co> >>>>>>>>> wrote: >>>>>>>>> >>>>>>>> The main argument for having it in core is: >>>>>>>>>> >>>>>>>>>> * It integrates directly with the Calendar behaviour >>>>>>>>>> * We could provide built-in sigils in the future to create >>>>>>>>>> readable durations, such as ~P[3 hours and 10 minutes] >>>>>>>>>> * Postgrex, Explorer, CLDR, etc all implement their own version >>>>>>>>>> of durations >>>>>>>>>> >>>>>>>>>> Arguments for not having it in core: it happens that all of the >>>>>>>>>> arguments above can also be solved without adding Duration to Elixir >>>>>>>>>> and, >>>>>>>>>> instead, by creating a custom library: >>>>>>>>>> >>>>>>>>>> * A separate library could extend the calendar behaviour with >>>>>>>>>> shift_* functions >>>>>>>>>> * Third-party sigils can also be provided by libraries >>>>>>>>>> * Postgrex, Explorer, and CLDR could create or use a package >>>>>>>>>> with a duratio type shared across them all >>>>>>>>>> >>>>>>>>>> I would love to hear the community thoughts. >>>>>>>>>> >>>>>>>>>> On Wed, Mar 6, 2024 at 7:16 PM 'Theo Fiedler' via >>>>>>>>>> elixir-lang-core <elixir-l...@googlegroups.com> wrote: >>>>>>>>>> >>>>>>>>> *Preface* >>>>>>>>>>> >>>>>>>>>>> We currently have `add/2-3` to manipulate calendar types in the >>>>>>>>>>> standard library. These functions allow adding a specified amount >>>>>>>>>>> of time >>>>>>>>>>> of given unit to a date/time. The standard library currently misses >>>>>>>>>>> means >>>>>>>>>>> to apply more complex, or logical *durations *to calendar >>>>>>>>>>> types. e.g. adding a month, a week, or one month and 10 days to a >>>>>>>>>>> date. >>>>>>>>>>> >>>>>>>>>>> *Reasons for it* >>>>>>>>>>> >>>>>>>>>>> While similar functionality exists in libraries, such as CLDR, >>>>>>>>>>> Timex, Tox, adding this functionality to the standard library has >>>>>>>>>>> already >>>>>>>>>>> been requested and discussed at multiple occasions over the past >>>>>>>>>>> years. To >>>>>>>>>>> list a few examples: >>>>>>>>>>> >>>>>>>>>>> - https://github.com/elixir-lang/elixir/pull/10199 >>>>>>>>>>> - >>>>>>>>>>> https://elixirforum.com/t/get-date-n-months-years-in-the-past/48346/3 >>>>>>>>>>> - >>>>>>>>>>> https://elixir-lang.slack.com/archives/C0HEX82NR/p1709581478427009?thread_ts=1709368588.334759&cid=C0HEX82NR >>>>>>>>>>> >>>>>>>>>>> Furthermore the shift behaviour in the extremely popular library >>>>>>>>>>> Timex changed <https://github.com/bitwalker/timex/issues/731> >>>>>>>>>>> in Elixir >= 1.14.3 which may have complicated the mostly lean and >>>>>>>>>>> non-breaking language upgrade Elixir has to offer. >>>>>>>>>>> >>>>>>>>>>> Elixir has a great set of modules and functions that deal with >>>>>>>>>>> date and time, the APIs are consistent and `shift/2-3` should fit >>>>>>>>>>> right in, >>>>>>>>>>> solving many standard needs of various industries, be it for >>>>>>>>>>> reporting, >>>>>>>>>>> appointments, events, finance... the list goes on, engineers >>>>>>>>>>> probably face >>>>>>>>>>> the need to shift time logically more often than not in their >>>>>>>>>>> careers. >>>>>>>>>>> >>>>>>>>>>> *Technical details* >>>>>>>>>>> >>>>>>>>>>> Duration >>>>>>>>>>> A date or time must be shifted by a *duration*. There is an ISO8601 >>>>>>>>>>> for durations <https://en.wikipedia.org/wiki/ISO_8601#Durations>, >>>>>>>>>>> which the initial implementation is loosely following. The >>>>>>>>>>> structure of a >>>>>>>>>>> Duration lives in its own module with its own set of functions to >>>>>>>>>>> create >>>>>>>>>>> and manipulate durations. One example of where it diverts from the >>>>>>>>>>> ISO >>>>>>>>>>> standard, is that it implements microseconds. Microseconds in a >>>>>>>>>>> *duration* are stored in the same format as in the time >>>>>>>>>>> calendar types, meaning they integrate well and provide consistency. >>>>>>>>>>> >>>>>>>>>>> Shift >>>>>>>>>>> The shift behaviour is implemented as a callback on Calendar and >>>>>>>>>>> supported by all calendar types: Date, DateTime, NaiveDateTime and >>>>>>>>>>> Time. >>>>>>>>>>> Date, Time and NaiveDateTime each have their own implementation of >>>>>>>>>>> a >>>>>>>>>>> "shift", while DateTime gets converted to a NaiveDateTime before >>>>>>>>>>> applying >>>>>>>>>>> the shift, and is then rebuilt to a DateTime in its original >>>>>>>>>>> timezone. >>>>>>>>>>> `shift/2-3` also has guaranteed output types (which isn't a given >>>>>>>>>>> in many >>>>>>>>>>> libraries) and follows the consistent API which is established in >>>>>>>>>>> the >>>>>>>>>>> calendar modules. >>>>>>>>>>> >>>>>>>>>>> Find the current state of the implementation here: >>>>>>>>>>> https://github.com/elixir-lang/elixir/pull/13385 >>>>>>>>>>> >>>>>>>>>>> *Benchmarks* >>>>>>>>>>> >>>>>>>>>>> There are some benchmarks + StreamData tests in the PR >>>>>>>>>>> description. >>>>>>>>>>> >>>>>>>>>>> *Outlook* >>>>>>>>>>> >>>>>>>>>>> *After *adding the Duration type and shift behaviour to the >>>>>>>>>>> standard library, the following things could be explored and >>>>>>>>>>> derived from >>>>>>>>>>> the initial work: >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> - Implementing a protocol that allows Duration to be applied >>>>>>>>>>> to any data type, not just dates and times. >>>>>>>>>>> - A range-like data type that allows us to do recurring >>>>>>>>>>> constructs on any data type. For example, >>>>>>>>>>> Duration.interval(~D[2000-01-01], >>>>>>>>>>> month: 1), when iterated, would emit {:ok, date} | {:error, >>>>>>>>>>> start, duration, reason} entries >>>>>>>>>>> - A sigil for easy creation of durations: ~P[3 hours and 10 >>>>>>>>>>> minutes] >>>>>>>>>>> - Making it so add/2-3 reuses the shift_* functions >>>>>>>>>>> >>>>>>>>>>> *Reasons against it* >>>>>>>>>>> >>>>>>>>>>> While I am convinced that adding `shift/2-3` to the standard >>>>>>>>>>> library would be very beneficial, nothing really speaks against the >>>>>>>>>>> points >>>>>>>>>>> mentioned above to be implemented in a library instead. However, >>>>>>>>>>> something >>>>>>>>>>> as crucial and central as date/time manipulation should still be >>>>>>>>>>> part of >>>>>>>>>>> the standard library, negating the risk of breaking changes, >>>>>>>>>>> inconsistent >>>>>>>>>>> behaviour and outdated or too unique ergonomics which aren't widely >>>>>>>>>>> applicable, unlike what should be part of the standard library. >>>>>>>>>>> >>>>>>>>>>> Many thanks to @jose & @kip for the initial reviews and everyone >>>>>>>>>>> in advance taking the time to read the proposal! >>>>>>>>>>> >>>>>>>>>>> Looking forward to hear other peoples ideas and opinions on the >>>>>>>>>>> subject! >>>>>>>>>>> >>>>>>>>>>> -- >>>>>>>>>>> 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/cb0ed628-3848-4de0-aa13-c0f4761e4d99n%40googlegroups.com >>>>>>>>>>> >>>>>>>>>>> <https://groups.google.com/d/msgid/elixir-lang-core/cb0ed628-3848-4de0-aa13-c0f4761e4d99n%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/CAGnRm4%2BNmFsMhbkRubMjnmM8c_Amq8DgmKCJtzJ1GEuM4-sVgw%40mail.gmail.com >>>>>>>>>> >>>>>>>>>> <https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4%2BNmFsMhbkRubMjnmM8c_Amq8DgmKCJtzJ1GEuM4-sVgw%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>>>>>>>> . >>>>>>>>>> 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