* bug#74965: Document date representations in calendar
@ 2024-12-19 8:39 Richard Lawrence
2024-12-19 8:46 ` bug#74965: [PATCH] Document representation of dates in calendar.el Richard Lawrence
0 siblings, 1 reply; 4+ messages in thread
From: Richard Lawrence @ 2024-12-19 8:39 UTC (permalink / raw)
To: 74965
Severity: minor
As discussed in this thread:
https://lists.gnu.org/archive/html/emacs-devel/2024-12/msg00291.html
it would be nice to have better documentation of the date
representations used by calendar.el. Opening a bug so I can send a patch
with a bug number.
^ permalink raw reply [flat|nested] 4+ messages in thread
* bug#74965: [PATCH] Document representation of dates in calendar.el
2024-12-19 8:39 bug#74965: Document date representations in calendar Richard Lawrence
@ 2024-12-19 8:46 ` Richard Lawrence
2024-12-21 11:01 ` Eli Zaretskii
2024-12-23 4:11 ` Richard Stallman
0 siblings, 2 replies; 4+ messages in thread
From: Richard Lawrence @ 2024-12-19 8:46 UTC (permalink / raw)
To: 74965
[-- Attachment #1: Type: text/plain, Size: 78 bytes --]
Tags: patch
Here is a patch documenting these representations in a comment.
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-Document-representation-of-dates-in-calendar.el.patch --]
[-- Type: text/patch, Size: 1694 bytes --]
From b81f80ca621836ff8a7bc6ae446f9abd1455d242 Mon Sep 17 00:00:00 2001
From: Richard Lawrence <rwl@recursewithless.net>
Date: Mon, 16 Dec 2024 20:46:34 +0100
Subject: [PATCH] Document representation of dates in calendar.el
* lisp/calendar/calendar.el: Add a comment in file header
explaining Gregorian and absolute representations of
dates. (Bug#74965)
---
lisp/calendar/calendar.el | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/lisp/calendar/calendar.el b/lisp/calendar/calendar.el
index 60d8fdd6aee..54b5aebbd8b 100644
--- a/lisp/calendar/calendar.el
+++ b/lisp/calendar/calendar.el
@@ -90,6 +90,23 @@
;; <https://doi.org/10.1002/spe.4380230404>
;; <http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.42.6421&rep=rep1&type=pdf>
+;; As described in more detail in that literature, a Gregorian calendar
+;; date in this file is represented as a list of integers (MONTH DAY YEAR).
+;; See the functions
+;; `calendar-extract-year',
+;; `calendar-extract-month', and
+;; `calendar-extract-day'
+;; which act as accessors for this representation.
+
+;; The calendar functions in this and related files also use an
+;; "absolute" representation, which is an integer number of days since
+;; December 31, 1BC on the Gregorian calendar. This representation is
+;; useful for certain calculations; e.g. `calendar-day-of-week' is
+;; simply the absolute represention modulo 7, because December 31, 1BC
+;; is a Sunday. The absolute representation is also to convert between
+;; different calendar scales: see e.g.
+;; `calendar-absolute-from-gregorian' in this file and
+;; `calendar-iso-from-absolute' in cal-iso.el.
;; A note on free variables:
--
2.39.5
^ permalink raw reply related [flat|nested] 4+ messages in thread
* bug#74965: [PATCH] Document representation of dates in calendar.el
2024-12-19 8:46 ` bug#74965: [PATCH] Document representation of dates in calendar.el Richard Lawrence
@ 2024-12-21 11:01 ` Eli Zaretskii
2024-12-23 4:11 ` Richard Stallman
1 sibling, 0 replies; 4+ messages in thread
From: Eli Zaretskii @ 2024-12-21 11:01 UTC (permalink / raw)
To: Richard Lawrence; +Cc: 74965-done
> From: Richard Lawrence <rwl@recursewithless.net>
> Date: Thu, 19 Dec 2024 09:46:49 +0100
>
> Here is a patch documenting these representations in a comment.
Thanks. Most of this I already installed using your previous patch.
So now I just added the missing info to what was already there. And
with that, I'm closing this bug.
^ permalink raw reply [flat|nested] 4+ messages in thread
* bug#74965: [PATCH] Document representation of dates in calendar.el
2024-12-19 8:46 ` bug#74965: [PATCH] Document representation of dates in calendar.el Richard Lawrence
2024-12-21 11:01 ` Eli Zaretskii
@ 2024-12-23 4:11 ` Richard Stallman
1 sibling, 0 replies; 4+ messages in thread
From: Richard Stallman @ 2024-12-23 4:11 UTC (permalink / raw)
To: Richard Lawrence; +Cc: 74965
[[[ To any NSA and FBI agents reading my email: please consider ]]]
[[[ whether defending the US Constitution against all enemies, ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]
Thanks for improving our code's readabilty.
There are other files in Emacs which could benefit from such improvement.
Would you ever be in hje mood to do more?
--
Dr Richard Stallman (https://stallman.org)
Chief GNUisance of the GNU Project (https://gnu.org)
Founder, Free Software Foundation (https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)
^ permalink raw reply [flat|nested] 4+ messages in thread
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2024-12-19 8:39 bug#74965: Document date representations in calendar Richard Lawrence
2024-12-19 8:46 ` bug#74965: [PATCH] Document representation of dates in calendar.el Richard Lawrence
2024-12-21 11:01 ` Eli Zaretskii
2024-12-23 4:11 ` Richard Stallman
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