Commit 4bd7ad5f authored by Glenn Morris's avatar Glenn Morris

(Commentary): Point to calendar.el.

(lunar-phase-list, lunar-new-moon-on-or-after): Reduce nesting of some lets.
parent c7af68bc
......@@ -27,8 +27,7 @@
;;; Commentary:
;; This collection of functions implements lunar phases for calendar.el and
;; diary.el.
;; See calendar.el.
;; Based on ``Astronomical Formulae for Calculators,'' 3rd ed., by Jean Meeus,
;; Willmann-Bell, Inc., 1985 and ``Astronomical Algorithms'' by Jean Meeus,
......@@ -39,10 +38,6 @@
;; The author would be delighted to have an astronomically more sophisticated
;; person rewrite the code for the lunar calculations in this file!
;; Technical details of all the calendrical calculations can be found in
;; ``Calendrical Calculations: The Millennium Edition'' by Edward M. Reingold
;; and Nachum Dershowitz, Cambridge University Press (2001).
;;; Code:
(require 'calendar)
......@@ -145,32 +140,33 @@ remainder mod 4 gives the phase: 0 new moon, 1 first quarter, 2 full moon,
(defun lunar-phase-list (month year)
"List of lunar phases for three months starting with Gregorian MONTH, YEAR."
(let ((end-month month)
(end-year year)
(start-month month)
(start-year year))
(increment-calendar-month end-month end-year 3)
(increment-calendar-month start-month start-year -1)
(let* ((end-date (list (list end-month 1 end-year)))
(start-date (list (list start-month
(let* ((end-month month)
(end-year year)
(start-month month)
(start-year year)
(end-date (progn
(increment-calendar-month end-month end-year 3)
(list (list end-month 1 end-year))))
(start-date (progn
(increment-calendar-month start-month start-year -1)
(list (list start-month
(calendar-last-day-of-month
start-month start-year)
start-year)))
(index (* 4
(truncate
start-year))))
(index (* 4 (truncate
(* 12.3685
(+ year
( / (calendar-day-number (list month 1 year))
366.0)
-1900)))))
(new-moon (lunar-phase index))
(list))
(while (calendar-date-compare new-moon end-date)
(if (calendar-date-compare start-date new-moon)
(setq list (append list (list new-moon))))
(setq index (1+ index)
new-moon (lunar-phase index)))
list)))
(new-moon (lunar-phase index))
list)
(while (calendar-date-compare new-moon end-date)
(if (calendar-date-compare start-date new-moon)
(setq list (append list (list new-moon))))
(setq index (1+ index)
new-moon (lunar-phase index)))
list))
(defun lunar-phase-name (phase)
"Name of lunar PHASE.
......@@ -375,17 +371,18 @@ as governed by the values of `calendar-daylight-savings-starts',
(year (+ (extract-calendar-year date)
(/ (calendar-day-number date) 365.25)))
(k (floor (* (- year 2000.0) 12.3685)))
(date (lunar-new-moon-time k)))
(while (< date d)
(setq k (1+ k)
date (lunar-new-moon-time k)))
(let* ((a-date (calendar-absolute-from-astro date))
(time (* 24 (- a-date (truncate a-date))))
(date (calendar-gregorian-from-absolute (truncate a-date)))
(adj (dst-adjust-time date time)))
(calendar-astro-from-absolute
(+ (calendar-absolute-from-gregorian (car adj))
(/ (cadr adj) 24.0))))))
(date (lunar-new-moon-time k))
(a-date (progn
(while (< date d)
(setq k (1+ k)
date (lunar-new-moon-time k)))
(calendar-absolute-from-astro date)))
(time (* 24 (- a-date (truncate a-date))))
(date (calendar-gregorian-from-absolute (truncate a-date)))
(adj (dst-adjust-time date time)))
(calendar-astro-from-absolute
(+ (calendar-absolute-from-gregorian (car adj))
(/ (cadr adj) 24.0)))))
(provide 'lunar)
......
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