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384 lines
15 KiB
EmacsLisp
384 lines
15 KiB
EmacsLisp
;;; cal-mayan.el --- calendar functions for the Mayan calendars.
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;; Copyright (C) 1992, 1993, 1995, 1997 Free Software Foundation, Inc.
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;; Author: Stewart M. Clamen <clamen@cs.cmu.edu>
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;; Edward M. Reingold <reingold@cs.uiuc.edu>
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;; Keywords: calendar
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;; Human-Keywords: Mayan calendar, Maya, calendar, diary
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software; you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation; either version 2, or (at your option)
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;; any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs; see the file COPYING. If not, write to the
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;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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;; Boston, MA 02111-1307, USA.
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;;; Commentary:
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;; This collection of functions implements the features of calendar.el and
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;; diary.el that deal with the Mayan calendar. It was written jointly by
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;; Stewart M. Clamen School of Computer Science
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;; clamen@cs.cmu.edu Carnegie Mellon University
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;; 5000 Forbes Avenue
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;; Pittsburgh, PA 15213
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;; and
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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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;; Comments, improvements, and bug reports should be sent to Reingold.
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;; Technical details of the Mayan calendrical calculations can be found in
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;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
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;; Cambridge University Press (1997), and in
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;; ``Calendrical Calculations, Part II: Three Historical Calendars''
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;; by E. M. Reingold, N. Dershowitz, and S. M. Clamen,
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;; Software--Practice and Experience, Volume 23, Number 4 (April, 1993),
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;; pages 383-404.
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;;; Code:
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(require 'calendar)
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(defconst calendar-mayan-days-before-absolute-zero 1137142
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"Number of days of the Mayan calendar epoch before absolute day 0.
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This is the Goodman-Martinez-Thompson correlation used by almost all experts,
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but some use 1137140. Using 1232041 gives you Spinden's correlation; using
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1142840 gives you Hochleitner's correlation.")
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(defconst calendar-mayan-haab-at-epoch '(8 . 18)
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"Mayan haab date at the epoch.")
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(defconst calendar-mayan-haab-month-name-array
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["Pop" "Uo" "Zip" "Zotz" "Tzec" "Xul" "Yaxkin" "Mol" "Chen" "Yax"
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"Zac" "Ceh" "Mac" "Kankin" "Muan" "Pax" "Kayab" "Cumku"])
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(defconst calendar-mayan-tzolkin-at-epoch '(4 . 20)
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"Mayan tzolkin date at the epoch.")
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(defconst calendar-mayan-tzolkin-names-array
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["Imix" "Ik" "Akbal" "Kan" "Chicchan" "Cimi" "Manik" "Lamat" "Muluc" "Oc"
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"Chuen" "Eb" "Ben" "Ix" "Men" "Cib" "Caban" "Etznab" "Cauac" "Ahau"])
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(defun calendar-mayan-long-count-from-absolute (date)
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"Compute the Mayan long count corresponding to the absolute DATE."
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(let ((long-count (+ date calendar-mayan-days-before-absolute-zero)))
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(let* ((baktun (/ long-count 144000))
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(remainder (% long-count 144000))
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(katun (/ remainder 7200))
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(remainder (% remainder 7200))
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(tun (/ remainder 360))
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(remainder (% remainder 360))
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(uinal (/ remainder 20))
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(kin (% remainder 20)))
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(list baktun katun tun uinal kin))))
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(defun calendar-mayan-long-count-to-string (mayan-long-count)
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"Convert MAYAN-LONG-COUNT into traditional written form."
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(apply 'format (cons "%s.%s.%s.%s.%s" mayan-long-count)))
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(defun calendar-string-to-mayan-long-count (str)
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"Given STR, a string of format \"%d.%d.%d.%d.%d\", return list of nums."
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(let ((rlc nil)
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(c (length str))
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(cc 0))
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(condition-case condition
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(progn
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(while (< cc c)
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(let* ((start (string-match "[0-9]+" str cc))
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(end (match-end 0))
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datum)
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(setq datum (read (substring str start end)))
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(setq rlc (cons datum rlc))
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(setq cc end)))
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(if (not (= (length rlc) 5)) (signal 'invalid-read-syntax nil)))
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(invalid-read-syntax nil))
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(reverse rlc)))
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(defun calendar-mayan-haab-from-absolute (date)
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"Convert absolute DATE into a Mayan haab date (a pair)."
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(let* ((long-count (+ date calendar-mayan-days-before-absolute-zero))
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(day-of-haab
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(% (+ long-count
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(car calendar-mayan-haab-at-epoch)
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(* 20 (1- (cdr calendar-mayan-haab-at-epoch))))
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365))
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(day (% day-of-haab 20))
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(month (1+ (/ day-of-haab 20))))
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(cons day month)))
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(defun calendar-mayan-haab-difference (date1 date2)
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"Number of days from Mayan haab DATE1 to next occurrence of haab date DATE2."
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(mod (+ (* 20 (- (cdr date2) (cdr date1)))
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(- (car date2) (car date1)))
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365))
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(defun calendar-mayan-haab-on-or-before (haab-date date)
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"Absolute date of latest HAAB-DATE on or before absolute DATE."
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(- date
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(% (- date
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(calendar-mayan-haab-difference
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(calendar-mayan-haab-from-absolute 0) haab-date))
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365)))
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(defun calendar-next-haab-date (haab-date &optional noecho)
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"Move cursor to next instance of Mayan HAAB-DATE.
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Echo Mayan date if NOECHO is t."
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(interactive (list (calendar-read-mayan-haab-date)))
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(calendar-goto-date
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(calendar-gregorian-from-absolute
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(calendar-mayan-haab-on-or-before
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haab-date
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(+ 365
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(calendar-absolute-from-gregorian (calendar-cursor-to-date))))))
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(or noecho (calendar-print-mayan-date)))
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(defun calendar-previous-haab-date (haab-date &optional noecho)
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"Move cursor to previous instance of Mayan HAAB-DATE.
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Echo Mayan date if NOECHO is t."
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(interactive (list (calendar-read-mayan-haab-date)))
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(calendar-goto-date
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(calendar-gregorian-from-absolute
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(calendar-mayan-haab-on-or-before
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haab-date
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(1- (calendar-absolute-from-gregorian (calendar-cursor-to-date))))))
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(or noecho (calendar-print-mayan-date)))
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(defun calendar-mayan-haab-to-string (haab)
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"Convert Mayan haab date (a pair) into its traditional written form."
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(let ((month (cdr haab))
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(day (car haab)))
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;; 19th month consists of 5 special days
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(if (= month 19)
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(format "%d Uayeb" day)
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(format "%d %s"
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day
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(aref calendar-mayan-haab-month-name-array (1- month))))))
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(defun calendar-mayan-tzolkin-from-absolute (date)
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"Convert absolute DATE into a Mayan tzolkin date (a pair)."
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(let* ((long-count (+ date calendar-mayan-days-before-absolute-zero))
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(day (calendar-mod
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(+ long-count (car calendar-mayan-tzolkin-at-epoch))
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13))
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(name (calendar-mod
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(+ long-count (cdr calendar-mayan-tzolkin-at-epoch))
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20)))
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(cons day name)))
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(defun calendar-mayan-tzolkin-difference (date1 date2)
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"Number of days from Mayan tzolkin DATE1 to next occurrence of tzolkin DATE2."
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(let ((number-difference (- (car date2) (car date1)))
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(name-difference (- (cdr date2) (cdr date1))))
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(mod (+ number-difference
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(* 13 (mod (* 3 (- number-difference name-difference))
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20)))
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260)))
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(defun calendar-mayan-tzolkin-on-or-before (tzolkin-date date)
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"Absolute date of latest TZOLKIN-DATE on or before absolute DATE."
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(- date
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(% (- date (calendar-mayan-tzolkin-difference
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(calendar-mayan-tzolkin-from-absolute 0)
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tzolkin-date))
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260)))
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(defun calendar-next-tzolkin-date (tzolkin-date &optional noecho)
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"Move cursor to next instance of Mayan TZOLKIN-DATE.
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Echo Mayan date if NOECHO is t."
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(interactive (list (calendar-read-mayan-tzolkin-date)))
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(calendar-goto-date
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(calendar-gregorian-from-absolute
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(calendar-mayan-tzolkin-on-or-before
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tzolkin-date
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(+ 260
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(calendar-absolute-from-gregorian (calendar-cursor-to-date))))))
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(or noecho (calendar-print-mayan-date)))
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(defun calendar-previous-tzolkin-date (tzolkin-date &optional noecho)
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"Move cursor to previous instance of Mayan TZOLKIN-DATE.
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Echo Mayan date if NOECHO is t."
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(interactive (list (calendar-read-mayan-tzolkin-date)))
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(calendar-goto-date
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(calendar-gregorian-from-absolute
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(calendar-mayan-tzolkin-on-or-before
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tzolkin-date
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(1- (calendar-absolute-from-gregorian (calendar-cursor-to-date))))))
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(or noecho (calendar-print-mayan-date)))
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(defun calendar-mayan-tzolkin-to-string (tzolkin)
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"Convert Mayan tzolkin date (a pair) into its traditional written form."
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(format "%d %s"
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(car tzolkin)
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(aref calendar-mayan-tzolkin-names-array (1- (cdr tzolkin)))))
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(defun calendar-mayan-tzolkin-haab-on-or-before (tzolkin-date haab-date date)
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"Absolute date that is Mayan TZOLKIN-DATE and HAAB-DATE.
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Latest such date on or before DATE.
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Returns nil if such a tzolkin-haab combination is impossible."
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(let* ((haab-difference
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(calendar-mayan-haab-difference
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(calendar-mayan-haab-from-absolute 0)
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haab-date))
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(tzolkin-difference
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(calendar-mayan-tzolkin-difference
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(calendar-mayan-tzolkin-from-absolute 0)
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tzolkin-date))
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(difference (- tzolkin-difference haab-difference)))
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(if (= (% difference 5) 0)
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(- date
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(mod (- date
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(+ haab-difference (* 365 difference)))
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18980))
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nil)))
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(defun calendar-read-mayan-haab-date ()
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"Prompt for a Mayan haab date"
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(let* ((completion-ignore-case t)
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(haab-day (calendar-read
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"Haab kin (0-19): "
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'(lambda (x) (and (>= x 0) (< x 20)))))
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(haab-month-list (append calendar-mayan-haab-month-name-array
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(and (< haab-day 5) '("Uayeb"))))
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(haab-month (cdr
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(assoc
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(capitalize
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(completing-read "Haab uinal: "
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(mapcar 'list haab-month-list)
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nil t))
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(calendar-make-alist
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haab-month-list 1 'capitalize)))))
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(cons haab-day haab-month)))
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(defun calendar-read-mayan-tzolkin-date ()
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"Prompt for a Mayan tzolkin date"
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(let* ((completion-ignore-case t)
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(tzolkin-count (calendar-read
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"Tzolkin kin (1-13): "
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'(lambda (x) (and (> x 0) (< x 14)))))
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(tzolkin-name-list (append calendar-mayan-tzolkin-names-array nil))
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(tzolkin-name (cdr
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(assoc
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(capitalize
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(completing-read "Tzolkin uinal: "
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(mapcar 'list tzolkin-name-list)
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nil t))
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(calendar-make-alist
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tzolkin-name-list 1 'capitalize)))))
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(cons tzolkin-count tzolkin-name)))
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(defun calendar-next-calendar-round-date
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(tzolkin-date haab-date &optional noecho)
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"Move cursor to next instance of Mayan HAAB-DATE TZOLKIN-DATE combination.
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Echo Mayan date if NOECHO is t."
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(interactive (list (calendar-read-mayan-tzolkin-date)
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(calendar-read-mayan-haab-date)))
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(let ((date (calendar-mayan-tzolkin-haab-on-or-before
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tzolkin-date haab-date
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(+ 18980 (calendar-absolute-from-gregorian
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(calendar-cursor-to-date))))))
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(if (not date)
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(error "%s, %s does not exist in the Mayan calendar round"
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(calendar-mayan-tzolkin-to-string tzolkin-date)
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(calendar-mayan-haab-to-string haab-date))
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(calendar-goto-date (calendar-gregorian-from-absolute date))
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(or noecho (calendar-print-mayan-date)))))
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(defun calendar-previous-calendar-round-date
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(tzolkin-date haab-date &optional noecho)
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"Move to previous instance of Mayan TZOLKIN-DATE HAAB-DATE combination.
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Echo Mayan date if NOECHO is t."
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(interactive (list (calendar-read-mayan-tzolkin-date)
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(calendar-read-mayan-haab-date)))
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(let ((date (calendar-mayan-tzolkin-haab-on-or-before
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tzolkin-date haab-date
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(1- (calendar-absolute-from-gregorian
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(calendar-cursor-to-date))))))
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(if (not date)
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(error "%s, %s does not exist in the Mayan calendar round"
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(calendar-mayan-tzolkin-to-string tzolkin-date)
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(calendar-mayan-haab-to-string haab-date))
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(calendar-goto-date (calendar-gregorian-from-absolute date))
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(or noecho (calendar-print-mayan-date)))))
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(defun calendar-absolute-from-mayan-long-count (c)
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"Compute the absolute date corresponding to the Mayan Long Count C.
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Long count is a list (baktun katun tun uinal kin)"
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(+ (* (nth 0 c) 144000) ; baktun
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(* (nth 1 c) 7200) ; katun
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(* (nth 2 c) 360) ; tun
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(* (nth 3 c) 20) ; uinal
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(nth 4 c) ; kin (days)
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(- ; days before absolute date 0
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calendar-mayan-days-before-absolute-zero)))
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(defun calendar-mayan-date-string (&optional date)
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"String of Mayan date of Gregorian DATE.
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Defaults to today's date if DATE is not given."
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(let* ((d (calendar-absolute-from-gregorian
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(or date (calendar-current-date))))
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(tzolkin (calendar-mayan-tzolkin-from-absolute d))
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(haab (calendar-mayan-haab-from-absolute d))
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(long-count (calendar-mayan-long-count-from-absolute d)))
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(format "Long count = %s; tzolkin = %s; haab = %s"
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(calendar-mayan-long-count-to-string long-count)
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(calendar-mayan-tzolkin-to-string tzolkin)
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(calendar-mayan-haab-to-string haab))))
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(defun calendar-print-mayan-date ()
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"Show the Mayan long count, tzolkin, and haab equivalents of date."
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(interactive)
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(message "Mayan date: %s"
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(calendar-mayan-date-string (calendar-cursor-to-date t))))
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(defun calendar-goto-mayan-long-count-date (date &optional noecho)
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"Move cursor to Mayan long count DATE. Echo Mayan date unless NOECHO is t."
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(interactive
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(let (lc)
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(while (not lc)
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(let ((datum
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(calendar-string-to-mayan-long-count
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(read-string "Mayan long count (baktun.katun.tun.uinal.kin): "
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(calendar-mayan-long-count-to-string
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(calendar-mayan-long-count-from-absolute
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(calendar-absolute-from-gregorian
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(calendar-current-date))))))))
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(if (calendar-mayan-long-count-common-era datum)
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(setq lc datum))))
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(list lc)))
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(calendar-goto-date
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(calendar-gregorian-from-absolute
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(calendar-absolute-from-mayan-long-count date)))
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(or noecho (calendar-print-mayan-date)))
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(defun calendar-mayan-long-count-common-era (lc)
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"T if long count represents date in the Common Era."
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(let ((base (calendar-mayan-long-count-from-absolute 1)))
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(while (and (not (null base)) (= (car lc) (car base)))
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(setq lc (cdr lc)
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base (cdr base)))
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(or (null lc) (> (car lc) (car base)))))
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(defun diary-mayan-date ()
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"Show the Mayan long count, haab, and tzolkin dates as a diary entry."
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(format "Mayan date: %s" (calendar-mayan-date-string date)))
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(provide 'cal-mayan)
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;;; cal-mayan.el ends here
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