bug#74869: Fwd: [PATCH] Add predicates for decoded times and time deltas

bug#74869: Fwd: [PATCH] Add predicates for decoded times and time deltas

[Paul Eggert]

Argh, I now see that I cc'ed the wrong bug report. It should be bug 
74869, not 74689. Forwarding this two-day-old email to the correct bug 
report. Sorry about the duplication.


-------- Forwarded Message --------
Subject: Re: [PATCH] Add predicates for decoded times and time deltas
Date: Fri, 27 Dec 2024 16:44:32 -0800
From: Paul Eggert <eggert@cs.ucla.edu>
To: Richard Lawrence <rwl@recursewithless.net>
CC: 74689@debbugs.gnu.org

What's the use case for these proposed predicates? I'm finding it hard 
to review the patch without knowing what it's for.

Surely this should be in time-date.el rather than simple.el.

The implementation of decoded-time-p seems complicated and doesn't match 
what decode-time produces. Wouldn't it be simpler to call (ignore-errors 
(equal val (decode-time (encode-time val))))?

bug#74869: Fwd: [PATCH] Add predicates for decoded times and time deltas

[Paul Eggert]

Forwarding another mis-addressed email of mine.


-------- Forwarded Message --------
Subject: Re: [PATCH] Add predicates for decoded times and time deltas
Date: Sat, 28 Dec 2024 09:26:23 -0800
From: Paul Eggert <eggert@cs.ucla.edu>
To: Richard Lawrence <rwl@recursewithless.net>
CC: 74689@debbugs.gnu.org

On 12/28/24 07:56, Richard Lawrence wrote:
> I need to use
> `calendar-extract-month' with a plain date value, but
> `decoded-time-month' with a date-time value. I need type predicates to
> do such dispatching.

Not necessarily; you can instead try each function in turn and use the 
first that works.

I have some qualms about saying that decoded times are a "type". Whether 
a decoded time is valid depends on the timezone: (0 30 2 10 3 2024 0 t 
-21600) is a valid decoded time in Phoenix but not in Denver, because 
clocks sprang forward over that time in Denver but not in Phoenix. When 
data interpretation gets that complicated, the Emacs notion of "type" is 
not always the best.