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#pike __REAL_VERSION__ 
 
//! This is the islamic calendar. Due to some sources, 
//! they decide the first day of the new months on a 
//! month-to-month basis (sightings of the new moon), 
//! so it's probably not @i{that@} accurate. If 
//! someone can confirm (or deny) accuracy better than that, 
//! please contact me so I can change this statement. 
//! 
//! It's vaugely based on rules presented in algorithms by 
//! Dershowitz, Reingold and Clamen, 'Calendrical Calculations'. 
//! It is the same that's used in Emacs calendar mode. 
//! 
//! @bugs 
//! I have currently no idea how the arabic countries 
//! count the week. Follow the same rules as @[ISO] 
//! for now... The time is also suspicious; the @b{day@} 
//! really starts at sunset and not midnight, 
//! the hours of the day is not correct. Also don't know 
//! what to call years before 1 - go for "BH"; positive 
//! years are "AH", anno Hegirac. 
 
inherit Calendar.YMD:YMD; 
 
#include "constants.h" 
 
string calendar_name() { return "Islamic"; } 
 
private protected mixed __initstuff=lambda() 
{ 
   f_week_day_shortname_from_number="islamic_week_day_shortname_from_number"; 
   f_week_day_name_from_number="islamic_week_day_name_from_number"; 
   f_year_name_from_number="islamic_year_name_from_number"; 
 
   f_month_day_name_from_number="month_day_name_from_number"; 
   f_month_name_from_number="islamic_month_name_from_number"; 
   f_month_shortname_from_number="islamic_month_shortname_from_number"; 
   f_month_number_from_name="islamic_month_number_from_name"; 
 
   f_week_day_number_from_name="gregorian_week_day_number_from_name"; 
   f_week_name_from_number="week_name_from_number"; 
}(); 
 
int year_leap_year(int y) 
{ 
   return (14+11*y)%30<11; 
} 
 
int julian_day_from_year(int y) 
{ 
   return (y-1)*354 + (11*y+3)/30 + 1948440; 
} 
 
array(int) year_from_julian_day(int jd) 
{ 
// [y,yjd] 
   jd-=1948440; 
   int tr=jd/10631; 
   int td=jd-tr*10631; 
   int y=(14+td*30)/10631+tr*30+1; 
 
   return ({y, 
            (y-1)*354 + (11*y+3)/30 + 1948440}); 
} 
 
protected array(int) year_month_from_month(int y,int m) 
{ 
// [y,m,ndays,myd] 
 
   y+=(m-1)/12; 
   m=1+(m-1)%12; 
 
   switch (m) 
   { 
      case  1: return ({y,m,30,  1}); 
      case  2: return ({y,m,29, 31}); 
      case  3: return ({y,m,30, 60}); 
      case  4: return ({y,m,29, 90}); 
      case  5: return ({y,m,30,119}); 
      case  6: return ({y,m,29,149}); 
      case  7: return ({y,m,30,178}); 
      case  8: return ({y,m,29,208}); 
      case  9: return ({y,m,30,237}); 
      case 10: return ({y,m,29,267}); 
      case 11: return ({y,m,30,296}); 
      case 12: return ({y,m,29+year_leap_year(y),326}); 
   } 
 
   error("Month out of range.\n"); 
} 
 
protected array(int) month_from_yday(int y,int yd) 
{ 
// [month,day-of-month,ndays,month-year-day] 
   int l=year_leap_year(y); 
 
   switch (yd) 
   { 
      case   1.. 30: return ({ 1,yd,    30,  1}); 
      case  31.. 59: return ({ 2,yd- 30,29, 31}); 
      case  60.. 89: return ({ 3,yd- 59,30, 60}); 
      case  90..118: return ({ 4,yd- 89,29, 90}); 
      case 119..148: return ({ 5,yd-118,30,119}); 
      case 149..177: return ({ 6,yd-148,29,149}); 
      case 178..207: return ({ 7,yd-177,30,178}); 
      case 208..236: return ({ 8,yd-207,29,208}); 
      case 237..266: return ({ 9,yd-236,30,237}); 
      case 267..295: return ({10,yd-266,29,267}); 
      case 296..325: return ({11,yd-295,30,296}); 
      case 326..:    return ({12,yd-326,29+year_leap_year(y),326}); 
   } 
 
   error("yday out of range.\n"); 
} 
 
protected array(int) week_from_julian_day(int jd) 
{ 
// [year,week,day-of-week,ndays,week-julian-day] 
 
   [int y,int yjd]=year_from_julian_day(jd); 
   int yday=jd-yjd+1; 
 
   int k=4+(yjd-4)%7; 
   int w=(yday+k)/7; 
   int wjd=jd-(jd+1)%7; 
 
// fixme: week number 
 
   return ({y,w,1+(yjd+yday)%7,7,wjd}); 
} 
 
protected array(int) week_from_week(int y,int w) 
{ 
// [year,week,1 (wd),ndays,week-julian-day] 
 
   int yjd=julian_day_from_year(y); 
   int wjd=-5+yjd-(yjd+3)%7; 
 
//   fixme: week number 
 
   return ({y,w,1,7,wjd+w*7}); 
} 
 
protected int compat_week_day(int n) 
{ 
   return n%7; 
} 
 
protected int year_remaining_days(int y,int yday) 
{ 
   return 354+year_leap_year(y)-yday; 
} 
 
class cYear 
{ 
   inherit YMD::cYear; 
 
   int number_of_days() 
   { 
      switch (n) 
      { 
         case 0: return 0; 
         case 1: return 354+leap_year(); 
         default: 
            return julian_day_from_year(y+n)-yjd; 
      } 
   } 
 
   int number_of_months() 
   { 
      return 12*n; 
   } 
 
   int number_of_weeks() 
   { 
      if (!n) return 1; 
//        if (n==1) return 51; 
      return 
         Week("julian",jd) 
         ->range(Week("julian",julian_day_from_year(y+n)-1)) 
         ->number_of_weeks(); 
   } 
 
   TimeRange place(TimeRange what,void|int force) 
   { 
      if (what->is_day) 
      { 
         int yd=what->yd; 
         if (yd==355 && !year_leap_year(y)) 
            if (!force) return 0; // can't place 
            else return Day("julian_r",julian_day_from_year(y+1),rules); 
         return Day("ymd_yd",rules,y,yjd,yjd+yd-1,yd,what->n); 
      } 
 
      return ::place(what,force); 
   } 
} 
 
class cDay 
{ 
   inherit YMD::cDay; 
 
   int number_of_months() 
   { 
      if (n<=1) return 1; 
      if (m==CALUNKNOWN) make_month(); 
      [int zy,int zyjd]=year_from_julian_day(jd+n-1); 
      [int zm,int zmd,int znd,int zmyd]=month_from_yday(zy,jd+n-zyjd); 
      return zm-m+1+(zy-y)*12; 
   } 
} 
 
class cMonth 
{ 
   inherit YMD::cMonth; 
 
   protected int months_to_month(int y2,int m2) 
   { 
      return (y2-y)*12+(m2-m); 
   } 
} 
 
class cWeek 
{ 
   inherit YMD::cWeek; 
 
   protected int weeks_to_week(int y2,int w2) 
   { 
      [int y3,int w3,int wd2,int nd2,int jd2]=week_from_week(y2,w2); 
      return (jd2-jd)/7; 
   } 
 
   int number_of_days() 
   { 
      return 7*n; 
   } 
}