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292 lines
12 KiB
EmacsLisp
292 lines
12 KiB
EmacsLisp
;;; lunar.el --- calendar functions for phases of the moon.
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;; Copyright (C) 1992 Free Software Foundation, Inc.
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;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
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;; Keywords: calendar
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;; Human-Keywords: moon, lunar phases, calendar, diary
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;; This file is part of GNU Emacs.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY. No author or distributor
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;; accepts responsibility to anyone for the consequences of using it
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;; or for whether it serves any particular purpose or works at all,
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;; unless he says so in writing. Refer to the GNU Emacs General Public
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;; License for full details.
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;; Everyone is granted permission to copy, modify and redistribute
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;; GNU Emacs, but only under the conditions described in the
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;; GNU Emacs General Public License. A copy of this license is
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;; supposed to have been given to you along with GNU Emacs so you
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;; can know your rights and responsibilities. It should be in a
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;; file named COPYING. Among other things, the copyright notice
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;; and this notice must be preserved on all copies.
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;;; Commentary:
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;; This collection of functions implements lunar phases for calendar.el and
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;; diary.el.
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;; Based on ``Astronomical Formulae for Calculators,'' 3rd ed., by Jean Meeus,
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;; Willmann-Bell, Inc., 1985.
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;;
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;; WARNING: The calculations will be accurate only to within a few minutes.
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;; The author would be delighted to have an astronomically more sophisticated
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;; person rewrite the code for the lunar calculations in this file!
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;; Comments, corrections, and improvements should be sent to
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;; Edward M. Reingold Department of Computer Science
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;; (217) 333-6733 University of Illinois at Urbana-Champaign
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;; reingold@cs.uiuc.edu 1304 West Springfield Avenue
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;; Urbana, Illinois 61801
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;;; Code:
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(if (fboundp 'atan)
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(require 'lisp-float-type)
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(error "Lunar calculations impossible since floating point is unavailable."))
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(require 'solar)
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(defun lunar-phase-list (month year)
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"List of lunar phases for three months starting with Gregorian MONTH, YEAR."
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(let ((end-month month)
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(end-year year)
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(start-month month)
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(start-year year))
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(increment-calendar-month end-month end-year 3)
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(increment-calendar-month start-month start-year -1)
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(let* ((end-date (list (list end-month 1 end-year)))
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(start-date (list (list start-month
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(calendar-last-day-of-month
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start-month start-year)
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start-year)))
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(index (* 4
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(truncate
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(* 12.3685
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(+ year
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( / (calendar-day-number (list month 1 year))
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366.0)
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-1900)))))
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(new-moon (lunar-phase index))
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(list))
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(while (calendar-date-compare new-moon end-date)
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(if (calendar-date-compare start-date new-moon)
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(setq list (append list (list new-moon))))
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(setq index (1+ index))
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(setq new-moon (lunar-phase index)))
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list)))
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(defun lunar-phase (index)
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"Local date and time of lunar phase INDEX.
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Integer below INDEX/4 gives the lunation number, counting from Jan 1, 1900;
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remainder mod 4 gives the phase: 0 new moon, 1 first quarter, 2 full moon,
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3 last quarter."
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(let* ((phase (% index 4))
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(index (/ index 4.0))
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(time (/ index 1236.85))
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(date (+ (calendar-absolute-from-gregorian '(1 0.5 1900))
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0.75933
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(* 29.53058868 index)
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(* 0.0001178 time time)
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(* -0.000000155 time time time)
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(* 0.00033
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(solar-sin-degrees (+ 166.56
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(* 132.87 time)
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(* -0.009173 time time))))))
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(sun-anomaly (solar-mod
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(+ 359.2242
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(* 29.105356 index)
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(* -0.0000333 time time)
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(* -0.00000347 time time time))
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360.0))
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(moon-anomaly (solar-mod
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(+ 306.0253
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(* 385.81691806 index)
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(* 0.0107306 time time)
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(* 0.00001236 time time time))
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360.0))
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(moon-lat (solar-mod
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(+ 21.2964
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(* 390.67050646 index)
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(* -0.0016528 time time)
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(* -0.00000239 time time time))
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360.0))
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(adjustment
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(if (memq phase '(0 2))
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(+ (* (- 0.1734 (* 0.000393 time))
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(solar-sin-degrees sun-anomaly))
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(* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
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(* -0.4068 (solar-sin-degrees moon-anomaly))
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(* 0.0161 (solar-sin-degrees (* 2 moon-anomaly)))
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(* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
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(* 0.0104 (solar-sin-degrees (* 2 moon-lat)))
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(* -0.0051 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
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(* -0.0074 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
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(* 0.0004 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
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(* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
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(* -0.0006 (solar-sin-degrees
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(+ (* 2 moon-lat) moon-anomaly)))
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(* 0.0010 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
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(* 0.0005 (solar-sin-degrees
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(+ (* 2 moon-anomaly) sun-anomaly))))
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(+ (* (- 0.1721 (* 0.0004 time))
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(solar-sin-degrees sun-anomaly))
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(* 0.0021 (solar-sin-degrees (* 2 sun-anomaly)))
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(* -0.6280 (solar-sin-degrees moon-anomaly))
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(* 0.0089 (solar-sin-degrees (* 2 moon-anomaly)))
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(* -0.0004 (solar-sin-degrees (* 3 moon-anomaly)))
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(* 0.0079 (solar-sin-degrees (* 2 moon-lat)))
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(* -0.0119 (solar-sin-degrees (+ sun-anomaly moon-anomaly)))
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(* -0.0047 (solar-sin-degrees (- sun-anomaly moon-anomaly)))
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(* 0.0003 (solar-sin-degrees (+ (* 2 moon-lat) sun-anomaly)))
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(* -0.0004 (solar-sin-degrees (- (* 2 moon-lat) sun-anomaly)))
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(* -0.0006 (solar-sin-degrees (+ (* 2 moon-lat) moon-anomaly)))
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(* 0.0021 (solar-sin-degrees (- (* 2 moon-lat) moon-anomaly)))
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(* 0.0003 (solar-sin-degrees
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(+ (* 2 moon-anomaly) sun-anomaly)))
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(* 0.0004 (solar-sin-degrees
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(- sun-anomaly (* 2 moon-anomaly))))
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(* -0.0003 (solar-sin-degrees
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(+ (* 2 sun-anomaly) moon-anomaly))))))
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(adj (+ 0.0028
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(* -0.0004 (solar-cosine-degrees
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sun-anomaly))
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(* 0.0003 (solar-cosine-degrees
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moon-anomaly))))
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(adjustment (cond ((= phase 1) (+ adjustment adj))
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((= phase 2) (- adjustment adj))
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(t adjustment)))
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(date (+ date adjustment))
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(calendar-standard-time-zone-name
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(if calendar-time-zone calendar-standard-time-zone-name "UT"))
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(calendar-daylight-savings-starts
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(if calendar-time-zone calendar-daylight-savings-starts))
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(calendar-daylight-savings-ends
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(if calendar-time-zone calendar-daylight-savings-ends))
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(calendar-time-zone (if calendar-time-zone calendar-time-zone 0))
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(year (extract-calendar-year
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(calendar-gregorian-from-absolute (truncate date))))
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(dst (and calendar-daylight-savings-starts
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calendar-daylight-savings-ends
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(<= (calendar-absolute-from-gregorian
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(eval calendar-daylight-savings-starts))
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date)
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(< date
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(calendar-absolute-from-gregorian
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(eval calendar-daylight-savings-ends)))))
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(date (+ date
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(/ (+ (if dst 60 0) calendar-time-zone) 60.0 24.0)
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(- (/ (solar-ephemeris-correction year) 60.0 24.0))))
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(time (* 24 (- date (truncate date))))
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(date (calendar-gregorian-from-absolute (truncate date)))
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(time-zone calendar-time-zone)
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(time-zone (if dst
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calendar-daylight-time-zone-name
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calendar-standard-time-zone-name))
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(24-hours (truncate time))
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(12-hours (format "%d" (if (> 24-hours 12)
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(- 24-hours 12)
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(if (= 24-hours 0) 12 24-hours))))
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(am-pm (if (>= 24-hours 12) "pm" "am"))
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(minutes (format "%02d" (round (* 60 (- time 24-hours)))))
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(24-hours (format "%02d" 24-hours))
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(time (mapconcat 'eval calendar-time-display-form "")))
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(list date time phase)))
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(defun lunar-phase-name (phase)
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"Name of lunar PHASE.
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0 = new moon, 1 = first quarter, 2 = full moon, 3 = last quarter."
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(cond ((= 0 phase) "New Moon")
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((= 1 phase) "First Quarter Moon")
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((= 2 phase) "Full Moon")
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((= 3 phase) "Last Quarter Moon")))
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(defun calendar-phases-of-moon ()
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"Create a buffer with the lunar phases for the current calendar window."
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(interactive)
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(message "Computing phases of the moon...")
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(let ((m1 displayed-month)
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(y1 displayed-year)
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(m2 displayed-month)
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(y2 displayed-year)
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(lunar-phases-buffer "*Phases of Moon*"))
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(increment-calendar-month m1 y1 -1)
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(increment-calendar-month m2 y2 1)
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(set-buffer (get-buffer-create lunar-phases-buffer))
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(setq buffer-read-only nil)
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(calendar-set-mode-line
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(format "Phases of the moon from %s, %d to %s, %d%%-"
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(calendar-month-name m1) y1 (calendar-month-name m2) y2))
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(erase-buffer)
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(insert
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(mapconcat
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'(lambda (x)
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(let ((date (car x))
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(time (car (cdr x)))
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(phase (car (cdr (cdr x)))))
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(concat (calendar-date-string date)
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": "
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(lunar-phase-name phase)
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" "
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time)))
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(lunar-phase-list m1 y1) "\n"))
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(goto-char (point-min))
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(set-buffer-modified-p nil)
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(setq buffer-read-only t)
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(display-buffer lunar-phases-buffer)
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(message "Computing phases of the moon...done")))
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;;;###autoload
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(defun phases-of-moon (&optional arg)
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"Display the quarters of the moon for last month, this month, and next month.
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If called with an optional prefix argument, prompts for month and year.
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This function is suitable for execution in a .emacs file."
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(interactive "P")
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(save-excursion
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(let* ((completion-ignore-case t)
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(date (calendar-current-date))
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(displayed-month
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(if arg
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(cdr (assoc
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(capitalize
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(completing-read
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"Month name: "
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(mapcar 'list (append calendar-month-name-array nil))
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nil t))
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(calendar-make-alist calendar-month-name-array)))
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(extract-calendar-month date)))
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(displayed-year
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(if arg
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(calendar-read
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"Year (>0): "
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'(lambda (x) (> x 0))
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(int-to-string
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(extract-calendar-year (calendar-current-date))))
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(extract-calendar-year date))))
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(calendar-phases-of-moon))))
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(defun diary-phases-of-moon ()
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"Moon phases diary entry."
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(let* ((index (* 4
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(truncate
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(* 12.3685
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(+ (extract-calendar-year date)
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( / (calendar-day-number date)
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366.0)
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-1900)))))
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(phase (lunar-phase index)))
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(while (calendar-date-compare phase (list date))
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(setq index (1+ index))
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(setq phase (lunar-phase index)))
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(if (calendar-date-equal (car phase) date)
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(concat (lunar-phase-name (car (cdr (cdr phase)))) " "
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(car (cdr phase))))))
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(provide 'lunar)
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;;; lunar.el ends here
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