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

[Paul Eggert <eggert@cs.ucla.edu>]

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.