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Commit 6ff099c3 authored by Edward M. Reingold's avatar Edward M. Reingold
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Allow vector form of latitude/longitude. Fix documentation.

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lisp/calendar/solar.el
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......@@ -25,8 +25,8 @@
;;; Commentary:
;; This collection of functions implements the features of calendar.el and
;; diary.el that deal with times of day, sunrise/sunset, and
;; This collection of functions implements the features of calendar.el,
;; diary.el, and holiday.el that deal with times of day, sunrise/sunset, and
;; eqinoxes/solstices.
;; Based on the ``Almanac for Computers 1984,'' prepared by the Nautical
......@@ -54,7 +54,7 @@
(if (fboundp 'atan)
(require 'lisp-float-type)
(error "Solar calculations impossible since floating point is unavailable."))
(error "Solar/lunar calculations impossible since floating point is unavailable."))
(require 'cal-dst)
......@@ -77,32 +77,69 @@ would give military-style times like `21:07 (UTC)'.")
;;;###autoload
(defvar calendar-latitude nil
"*Latitude of `calendar-location-name' in degrees, + north, - south.
For example, 40.7 for New York City.
It may not be a good idea to set this in advance for your site;
if there may be users running Emacs at your site
who are physically located elsewhere, they would get the wrong
value and might not know how to override it.")
"*Latitude of `calendar-location-name' in degrees.
The value can be either a decimal fraction (one place of accuracy is
sufficient), + north, - south, such as 40.7 for New York City, or the value
can be a vector [degrees minutes north/south] such as [40 50 north] for New
York City.
This variable should be set in site-local.el.")
;;;###autoload
(defvar calendar-longitude nil
"*Longitude of `calendar-location-name' in degrees, + east, - west.
For example, -74.0 for New York City.
It may not be a good idea to set this in advance for your site;
if there may be users running Emacs at your site
who are physically located elsewhere, they would get the wrong
value and might not know how to override it.")
"*Longitude of `calendar-location-name' in degrees.
The value can be either a decimal fraction (one place of accuracy is
sufficient), + east, - west, such as -73.9 for New York City, or the value
can be a vector [degrees minutes east/west] such as [73 55 west] for New
York City.
This variable should be set in site-local.el.")
(defsubst calendar-latitude ()
"Convert calendar-latitude to a signed decimal fraction, if needed."
(if (numberp calendar-latitude)
calendar-latitude
(let ((lat (+ (aref calendar-latitude 0)
(/ (aref calendar-latitude 1) 60.0))))
(if (equal (aref calendar-latitude 2) 'north)
lat
(- lat)))))
(defsubst calendar-longitude ()
"Convert calendar-longitude to a signed decimal fraction, if needed."
(if (numberp calendar-longitude)
calendar-longitude
(let ((long (+ (aref calendar-longitude 0)
(/ (aref calendar-longitude 1) 60.0))))
(if (equal (aref calendar-longitude 2) 'east)
long
(- long)))))
;;;###autoload
(defvar calendar-location-name
'(let ((float-output-format "%.1f"))
(format "%s%s, %s%s"
(abs calendar-latitude)
(if (> calendar-latitude 0) "N" "S")
(abs calendar-longitude)
(if (> calendar-longitude 0) "E" "W")))
(if (numberp calendar-latitude)
(abs calendar-latitude)
(+ (aref calendar-latitude 0)
(/ (aref calendar-latitude 1) 60.0)))
(if (numberp calendar-latitude)
(if (> calendar-latitude 0) "N" "S")
(if (equal (aref calendar-latitude 2) 'north) "N" "S"))
(if (numberp calendar-longitude)
(abs calendar-longitude)
(+ (aref calendar-longitude 0)
(/ (aref calendar-longitude 1) 60.0)))
(if (numberp calendar-longitude)
(if (> calendar-longitude 0) "E" "W")
(if (equal (aref calendar-latitude 2) 'east) "E" "W"))))
"*Expression evaluating to name of `calendar-longitude', calendar-latitude'.
Default value is just the latitude, longitude pair.")
For example, \"New York City\". Default value is just the latitude, longitude
pair.
This variable should be set in site-local.el.")
(defvar solar-n-hemi-seasons
'("Vernal Equinox" "Summer Solstice" "Autumnal Equinox" "Winter Solstice")
......@@ -135,10 +172,10 @@ Returns nil if nothing was entered."
(if (not (string-equal x ""))
(string-to-int x))))
(defun solar-sin-degrees (x)
(defsubst solar-sin-degrees (x)
(sin (degrees-to-radians x)))
(defun solar-cosine-degrees (x)
(defsubst solar-cosine-degrees (x)
(cos (degrees-to-radians x)))
(defun solar-tangent-degrees (x)
......@@ -182,11 +219,11 @@ Returns nil if nothing was entered."
(defconst solar-earth-orbit-eccentricity 0.016718
"Eccentricity of orbit of the earth around the sun.")
(defmacro solar-degrees-to-hours (deg)
(list '/ deg 15.0))
(defsubst solar-degrees-to-hours (deg)
(/ deg 15.0))
(defmacro solar-hours-to-days (hour)
(list '/ hour 24.0))
(defsubst solar-hours-to-days (hour)
(/ hour 24.0))
(defun solar-longitude-of-sun (day)
"Longitude of the sun at DAY in the year."
......@@ -221,7 +258,7 @@ that location on that day."
(approx-sunrise
(+ day-of-year
(solar-hours-to-days
(- 6 (solar-degrees-to-hours calendar-longitude)))))
(- 6 (solar-degrees-to-hours (calendar-longitude))))))
(solar-longitude-of-sun-at-sunrise
(solar-longitude-of-sun approx-sunrise))
(solar-right-ascension-at-sunrise
......@@ -231,9 +268,9 @@ that location on that day."
(cos-local-sunrise
(/ (- (solar-cosine-degrees (+ 90 (/ 50.0 60.0)))
(* (solar-sin-degrees solar-declination-at-sunrise)
(solar-sin-degrees calendar-latitude)))
(solar-sin-degrees (calendar-latitude))))
(* (solar-cosine-degrees solar-declination-at-sunrise)
(solar-cosine-degrees calendar-latitude)))))
(solar-cosine-degrees (calendar-latitude))))))
(if (<= (abs cos-local-sunrise) 1);; otherwise, no sunrise that day
(let* ((local-sunrise (solar-degrees-to-hours
(- 360 (solar-arccos cos-local-sunrise))))
......@@ -242,7 +279,7 @@ that location on that day."
(+ (* 0.065710 approx-sunrise)
6.622))
24)))
(+ (- local-mean-sunrise (solar-degrees-to-hours calendar-longitude))
(+ (- local-mean-sunrise (solar-degrees-to-hours (calendar-longitude)))
(/ calendar-time-zone 60.0))))))
(defun solar-sunset (date)
......@@ -256,7 +293,7 @@ that location on that day."
(approx-sunset
(+ day-of-year
(solar-hours-to-days
(- 18 (solar-degrees-to-hours calendar-longitude)))))
(- 18 (solar-degrees-to-hours (calendar-longitude))))))
(solar-longitude-of-sun-at-sunset
(solar-longitude-of-sun approx-sunset))
(solar-right-ascension-at-sunset
......@@ -266,9 +303,9 @@ that location on that day."
(cos-local-sunset
(/ (- (solar-cosine-degrees (+ 90 (/ 50.0 60.0)))
(* (solar-sin-degrees solar-declination-at-sunset)
(solar-sin-degrees calendar-latitude)))
(solar-sin-degrees (calendar-latitude))))
(* (solar-cosine-degrees solar-declination-at-sunset)
(solar-cosine-degrees calendar-latitude)))))
(solar-cosine-degrees (calendar-latitude))))))
(if (<= (abs cos-local-sunset) 1);; otherwise, no sunset that day
(let* ((local-sunset (solar-degrees-to-hours
(solar-arccos cos-local-sunset)))
......@@ -276,7 +313,7 @@ that location on that day."
(mod (- (+ local-sunset solar-right-ascension-at-sunset)
(+ (* 0.065710 approx-sunset) 6.622))
24)))
(+ (- local-mean-sunset (solar-degrees-to-hours calendar-longitude))
(+ (- local-mean-sunset (solar-degrees-to-hours (calendar-longitude)))
(/ calendar-time-zone 60.0))))))
(defun solar-adj-time-for-dst (date time &optional style)
......@@ -441,10 +478,21 @@ This function is suitable for execution in a .emacs file."
(if (< arg 16) calendar-location-name
(let ((float-output-format "%.1f"))
(format "%s%s, %s%s"
(abs calendar-latitude)
(if (> calendar-latitude 0) "N" "S")
(abs calendar-longitude)
(if (> calendar-longitude 0) "E" "W")))))
(if (numberp calendar-latitude)
(abs calendar-latitude)
(+ (aref calendar-latitude 0)
(/ (aref calendar-latitude 1) 60.0)))
(if (numberp calendar-latitude)
(if (> calendar-latitude 0) "N" "S")
(if (equal (aref calendar-latitude 2) 'north) "N" "S"))
(if (numberp calendar-longitude)
(abs calendar-longitude)
(+ (aref calendar-longitude 0)
(/ (aref calendar-longitude 1) 60.0)))
(if (numberp calendar-longitude)
(if (> calendar-longitude 0) "E" "W")
(if (equal (aref calendar-latitude 2) 'east)
"E" "W"))))))
(calendar-standard-time-zone-name
(if (< arg 16) calendar-standard-time-zone-name
(cond ((= calendar-time-zone 0) "UTC")
......@@ -522,7 +570,7 @@ Requires floating point."
(calendar-time-zone (if calendar-time-zone calendar-time-zone 0))
(k (1- (/ m 3)))
(date (solar-equinoxes/solstices k y))
(s-hemi (and calendar-latitude (< calendar-latitude 0)))
(s-hemi (and calendar-latitude (< (calendar-latitude) 0)))
(day (extract-calendar-day date))
(adj (solar-adj-time-for-dst
(list (extract-calendar-month date)
......
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