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Fix asr calculation and adding a new extreme calculation method #3

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May 17, 2014
Merged

Fix asr calculation and adding a new extreme calculation method #3

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46 changes: 29 additions & 17 deletions libs/prayertime/prayer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -49,7 +49,8 @@ enum exmethods { NONE_EX,
HALF_INVALID,
MIN_ALWAYS,
MIN_INVALID,
GOOD_INVALID_SAME };
GOOD_INVALID_SAME,
ANGLE_BASED };

enum methods { NONE,
EGYPT_SURVEY,
Expand Down Expand Up @@ -158,8 +159,12 @@ static void getPrayerTimesByDay ( const Location* loc, const Method* conf,
else tempPrayer[5] = zu + is;


/* Calculate all prayer times as Base-10 numbers in Extreme Latitudes (if
* needed) */
/* Re-calculate Fajr and Ishaa in Extreme Latitudes */
if (lat > conf->nearestLat) {
tempPrayer[0] = 99;
tempPrayer[5] = 99;
invalid = 1;
}

/* Reset status of extreme switches */
for (i=0; i<6; i++)
Expand All @@ -183,6 +188,18 @@ static void getPrayerTimesByDay ( const Location* loc, const Method* conf,

switch(conf->extreme)
{
/* Angle Based */
case ANGLE_BASED:
portion = ((24 - tempPrayer[4]) + tempPrayer[1]);
double fajrDiff = (1/60.0 * conf->fajrAng) * portion;
double ishaDiff = (1/60.0 * conf->ishaaAng) * portion;

tempPrayer[0] = tempPrayer[1] - fajrDiff;
tempPrayer[5] = tempPrayer[4] + ishaDiff;
pt[0].isExtreme = 1;
pt[5].isExtreme = 1;
break;

/* Nearest Latitude (Method.nearestLat) */
case LAT_ALL:
case LAT_ALWAYS:
Expand Down Expand Up @@ -608,24 +625,19 @@ static double getZuhr(double lon, const Astro* astro)

static double getAssr(double lat, double dec, int mathhab)
{
double part1, part2, part3, part4, ndec;
double part1, part2, part3, part4;
double rlat = DEG_TO_RAD(lat);

part1 = mathhab + tan(fabs(rlat - dec));
part2 = atan(1.0 / part1);

/* Reverse if at or near the southern hemisphere */
ndec = dec;
if (lat < 0.0)
ndec = -dec;
part1 = mathhab + tan(rlat - ndec);
if (part1 < 1.0)
part1 = mathhab - tan(rlat - ndec);

part2 = (PI/2.0) - atan(part1);
/* Compute the hour angle */
part3 = sin(part2) - (sin(rlat) * sin(ndec));
part4 = (part3 / (cos(rlat) * cos(ndec)));

if ( part4 < -INVALID_TRIGGER || part4 > INVALID_TRIGGER)
part3 = sin(part2) - (sin(rlat) * sin(dec));
part4 = (part3 / (cos(rlat) * cos(dec)));
if ( part4 < -INVALID_TRIGGER || part4 > INVALID_TRIGGER) {
return 99;
}

return DEG_TO_10_BASE * RAD_TO_DEG (acos(part4));
}
Expand Down
3 changes: 2 additions & 1 deletion libs/prayertime/prayer.h
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Expand Up @@ -126,7 +126,8 @@ extern "C" {
11: Half of the Night: Fajr Ishaa if invalid
12: Minutes from Shorooq/Maghrib: Fajr Ishaa Always (e.g. Maghrib=Ishaa)
13: Minutes from Shorooq/Maghrib: Fajr Ishaa If invalid

14: Nearest Good Day: Fajr Ishaa if either is invalid
15: Angle based: Fajr Ishaa if invalid
*/


Expand Down