I guess I'm queasy at the thought of a solution that simply does not raise an error. It should obey some basic laws of math. For example, subtracting a month, then adding it back on should yield the same date. This solution would not.
I'm in favor of eliminating month arithmetic. It doesn't add anything. Alternatively, we could leave it in, but require the user to catch any exceptions, then make up his/her mind what the semantics should be. -tk On Thu, Sep 19, 2019 at 6:25 AM mph <[email protected]> wrote: > Hi all, > > the primary requirement is: „Do not generate errors on month_delta > mathematics“ > > The implementation and thus resulting date is not so important, I think. > > So if we will implement any error-free logic, then everything will be ok. > > > > In my opinion, if the user has date say Mar 10th, or 03/10 and wants to > subtract one month, it just wants to do MM=03-1 -> 02/10. If the formula > generates invalid date (03/31 -> 02/31) then we should offer a valid date, > e.g. 02/28. Nothing more special. > For general use the implementation of any existing logic (bash) should be > acceptable. > > Thank you > > Pavel > > > Dne čtvrtek 19. září 2019 15:00:20 UTC+2 Thomas Keffer napsal(a): >> >> On Wed, Sep 18, 2019 at 11:37 PM gjr80 <[email protected]> wrote: >> >>> That aside, whether you call it a bug or not I don't think we should >>> have a tag that when you give it an allowed value/parameter it aborts the >>> template. >>> >> >> We don't. The tag that caused the error was user-supplied. >> >> From Graham's experiments, it looks like sqlite and bash simply subtract >> four weeks. The span tag can already do that, so if that's what the user >> wants, s/he can just specify it. >> >> As for Python, it doesn't even offer month arithmetic (at least, through >> class datetime.timedelta), probably for the reasons we have discovered. >> I'm thinking we should do the same. >> >> -tk >> >> > -- > You received this message because you are subscribed to the Google Groups > "weewx-user" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/weewx-user/36ad9d07-b295-4733-b0b2-44c9437133cd%40googlegroups.com > <https://groups.google.com/d/msgid/weewx-user/36ad9d07-b295-4733-b0b2-44c9437133cd%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/weewx-user/CAPq0zEAEepQSt0P3SXNfD17AeMLKR34x%3DqMTd8GbgZWM-d10AA%40mail.gmail.com.
