From: Ken Bloom <kbloom@...>
Date: 2007-08-14T23:40:05+09:00
Subject: Re: Any Muslims around?

On Tue, 14 Aug 2007 20:50:02 +0900, Kyrre Nyg奪rd wrote:

> Just wondering if any Muslims have gotten around to making a Ruby script
> that like plays a sound or something when it's time for prayer.
> 
> Thanks,
> Kyrre Nyg奪rd

Would this help? I use it as part of a suite of scripts for computing 
times that Orthodox Jews use to compute times for prayer. The algorithm 
comes from the US Naval Observatory's Almanac for Computers.

--Ken



require 'date'
require 'mathn'

#methods stolen from ruby-doc.org
class Date
   def to_datetime() DateTime.new0(self.class.jd_to_ajd(jd, 0, 0), @of, 
@sg) end
   def to_date() self end
   def to_time() Time.local(year, mon, mday) end
end
class DateTime
  def to_date() Date.new0(self.class.jd_to_ajd(jd, 0, 0), 0, @sg) end
  def to_datetime() self end
  def to_time
    d = new_offset(0)
    d.instance_eval do
      Time.utc(year, mon, mday, hour, min, sec,
               (sec_fraction * 86400000000).to_i)
    end.
        getlocal
  end  
end

#end stolen

def dms(degrees,minutes,seconds)
   degrees+minutes/60+seconds/60/60
end

module Sunrise
   include Math
   class Location
      attr_accessor :latitude, :longitude, :offset
      def initialize(latitude,longitude)
	 @latitude,@longitude=latitude,longitude
      end
   end

   def toRad(degrees)
      degrees*PI/180
   end

   def toDeg(radians)
      radians*180/PI
   end

   def sun_rise_set(which,date,location,zenith)
      #step 1: first calculate the day of the year
      n=date.yday

      #step 2: convert the longitude to hour value and calculate an 
approximate time
      lngHour=location.longitude/15
      t=n+ ((6-lngHour)/24) if which==:sunrise
      t=n+ ((18-lngHour)/24) if which==:sunset

      #step 3: calculate the sun's mean anomaly
      m=(0.9856 * t) - 3.289

      #step 4: calculate the sun's true longitude
      l=  (m+(1.1916 * sin(toRad(m))) + (0.020 * sin(toRad(2*m))) + 
282.634) % 360

      #step 5a: calculate the sun's right ascension
      ra = toDeg(atan(0.91764 * tan(toRad(l)))) % 360
      ###step 5b: right ascension value needs to be in the same quadrant 
as L
      lquadrant = (l/90).floor*90
      raquadrant = (ra/90).floor*90
      ra=ra+(lquadrant-raquadrant)

      #step 5c: right ascension value needs to be converted into hours
      ra/=15

      #step 6: calculate the sun's declination
      sinDec = 0.39782 * sin(toRad(l))
      cosDec = cos(asin(sinDec))
      #step 7a: calculate the sun's local hour angle
      cosH = (cos(toRad(zenith)) - (sinDec * sin(toRad
(location.latitude)))) / (cosDec * cos(toRad(location.latitude)))

      return nil if (not (-1..1).include? cosH)

      #step 7b: finish calculating H and convert into hours
      h = (360 - toDeg(acos(cosH)))/15 if which==:sunrise
      h = (toDeg(acos(cosH)))/15       if which==:sunset
      #step 8: calculate local mean time
      t = h + ra - (0.06571 * t) - 6.622
      t %=24
      #step 9: convert to UTC
      return date.to_datetime+(t - lngHour)/24
   end

   private :sun_rise_set

   def sunrise(date,location,zenith=90.8333)
      sun_rise_set :sunrise,date,location,zenith
   end
   def sunset(date,location,zenith=90.8333)
      sun_rise_set :sunset,date,location,zenith
   end
end


-- 
Ken Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/