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Turn repetitive code into a table
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@ebraminio
ebraminio committed Dec 31, 2021
1 parent 73c2f63 commit b65ff5e
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126 changes: 64 additions & 62 deletions src/main/java/io/github/persiancalendar/Equinox.java
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Original file line number Diff line number Diff line change
Expand Up @@ -9,8 +9,8 @@
////// 6.5.2012
// Its API is improved by ideas from https://github.com/MenoData/Time4J/blob/78cd60d6/base/src/main/java/net/time4j/calendar/astro/AstronomicalSeason.java

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.TimeZone;

public enum Equinox {
Expand All @@ -31,81 +31,83 @@ public enum Equinox {
*/
SOUTHERN_SOLSTICE;

// One degree expressed in radians
private final static double degrees = Math.PI / 180d;
// Meeus - Astronomical Algorithms - p179, Table 27.C
private final static double[][] equinoxTerms = {
{485, 324.96, 1934.136},
{203, 337.23, 32964.467},
{199, 342.08, 20.186},
{182, 27.85, 445267.112},
{156, 73.14, 45036.886},
{136, 171.52, 22518.443},
{77, 222.54, 65928.934},
{74, 296.72, 3034.906},
{70, 243.58, 9037.513},
{58, 119.81, 33718.147},
{52, 297.17, 150.678},
{50, 21.02, 2281.226},
{45, 247.54, 29929.562},
{44, 325.15, 31555.956},
{29, 60.93, 4443.417},
{18, 155.12, 67555.328},
{17, 288.79, 4562.452},
{16, 198.04, 62894.029},
{14, 199.76, 31436.921},
{12, 95.39, 14577.848},
{12, 287.11, 31931.756},
{12, 320.81, 34777.259},
{9, 227.73, 1222.114},
{8, 15.45, 16859.074}
};

private static double tableFormula(double x) {
private static double periodic24(double x) {
double result = 0;
// TODO: Replace with a table and a loop
result += 485 * Math.cos(degrees * (324.96 + x * 1934.136));
result += 203 * Math.cos(degrees * (337.23 + x * 32964.467));
result += 199 * Math.cos(degrees * (342.08 + x * 20.186));
result += 182 * Math.cos(degrees * (27.85 + x * 445267.112));
result += 156 * Math.cos(degrees * (73.14 + x * 45036.886));
result += 136 * Math.cos(degrees * (171.52 + x * 22518.443));
result += 77 * Math.cos(degrees * (222.54 + x * 65928.934));
result += 74 * Math.cos(degrees * (296.72 + x * 3034.906));
result += 70 * Math.cos(degrees * (243.58 + x * 9037.513));
result += 58 * Math.cos(degrees * (119.81 + x * 33718.147));
result += 52 * Math.cos(degrees * (297.17 + x * 150.678));
result += 50 * Math.cos(degrees * (21.02 + x * 2281.226));
result += 45 * Math.cos(degrees * (247.54 + x * 29929.562));
result += 44 * Math.cos(degrees * (325.15 + x * 31555.956));
result += 29 * Math.cos(degrees * (60.93 + x * 4443.417));
result += 18 * Math.cos(degrees * (155.12 + x * 67555.328));
result += 17 * Math.cos(degrees * (288.79 + x * 4562.452));
result += 16 * Math.cos(degrees * (198.04 + x * 62894.029));
result += 14 * Math.cos(degrees * (199.76 + x * 31436.921));
result += 12 * Math.cos(degrees * (95.39 + x * 14577.848));
result += 12 * Math.cos(degrees * (287.11 + x * 31931.756));
result += 12 * Math.cos(degrees * (320.81 + x * 34777.259));
result += 9 * Math.cos(degrees * (227.73 + x * 1222.114));
result += 8 * Math.cos(degrees * (15.45 + x * 16859.074));
for (double[] term : equinoxTerms)
result += term[0] * Math.cos(Math.PI / 180d * (term[1] + x * term[2]));
return result;
}

public Date inYear(int year) {
double y = (year - 2000) / 1000d;
double a = 0;
private double jdMean(int year) {
// Meeus - Astronomical Algorithms - p178, Table 27.B
final double y = (year - 2000) / 1000.0;
switch (this) {
case NORTHWARD_EQUINOX:
a = 2451623.80984 + 365242.37404 * y + .05169 * y * y - .00411 * y * y * y - .00057 * y * y * y * y;
break;
return 2451623.80984 + (365242.37404 + (.05169 + (-.00411 - .00057 * y) * y) * y) * y;
case NORTHERN_SOLSTICE:
a = 2451716.56767 + 365241.62603 * y + .00325 * y * y + .00888 * y * y * y - .00030 * y * y * y * y;
break;
return 2451716.56767 + (365241.62603 + (.00325 + (.00888 - .00030 * y) * y) * y) * y;
case SOUTHWARD_EQUINOX:
a = 2451810.21715 + 365242.01767 * y - .11575 * y * y + .00337 * y * y * y + .00078 * y * y * y * y;
break;
return 2451810.21715 + (365242.01767 + (-.11575 + (.00337 + .00078 * y) * y) * y) * y;
default:
case SOUTHERN_SOLSTICE:
a = 2451900.05952 + 365242.74049 * y - .06223 * y * y - .00823 * y * y * y + .00032 * y * y * y * y;
break;
return 2451900.05952 + (365242.74049 + (-.06223 + (-.00823 + .00032 * y) * y) * y) * y;
}
}

double b = (a - 2451545) / 36525d;
double c = (35999.373 * b - 2.47) * degrees;
double d = a + (.00001 * tableFormula(b)) / (1 + 0.0334 * Math.cos(c) + 0.0007 * Math.cos(2 * c))
public Date inYear(int year) {
final double a = jdMean(year);
final double b = (a - 2451545) / 36525d;
final double c = (35999.373 * b - 2.47) * Math.PI / 180d;
final double d = a + (.00001 * periodic24(b)) / (1 + 0.0334 * Math.cos(c) + 0.0007 * Math.cos(2 * c))
- (66 + year - 2000) / 86400d;
double e = Math.round(d);
double f = Math.floor((e - 1867216.25) / 36524.25);
double g = e + f - Math.floor(f / 4) + 1525d;
double h = Math.floor((g - 122.1) / 365.25);
double i = 365 * h + Math.floor(h / 4);
double k = Math.floor((g - i) / 30.6001);
double l = 24 * (d + .5 - e);
int day = (int) (Math.round(g - i) - Math.floor(30.6001 * k));
double month = k - 1 - 12 * Math.floor(k / 14);
int millisInDay = (int) Math.round(l * 60 * 60 * 1000);
final double e = Math.round(d);
final double f = Math.floor((e - 1867216.25) / 36524.25);
final double g = e + f - Math.floor(f / 4) + 1525d;
final double h = Math.floor((g - 122.1) / 365.25);
final double i = 365 * h + Math.floor(h / 4);
final double k = Math.floor((g - i) / 30.6001);
final double l = 24 * (d + .5 - e);
final int day = (int) (Math.round(g - i) - Math.floor(30.6001 * k));
final double month = k - 1 - 12 * Math.floor(k / 14);
final int millisInDay = (int) Math.round(l * 60 * 60 * 1000);

Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
calendar.set(Calendar.YEAR, year);
calendar.set(Calendar.MONTH, (int) month - 1);
calendar.set(Calendar.DAY_OF_MONTH, day);
calendar.set(Calendar.HOUR_OF_DAY, 0);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);
calendar.set(Calendar.MILLISECOND, 0);
calendar.add(Calendar.MILLISECOND, millisInDay);
final GregorianCalendar calendar = new GregorianCalendar(TimeZone.getTimeZone("UTC"));
calendar.set(GregorianCalendar.YEAR, year);
calendar.set(GregorianCalendar.MONTH, (int) month - 1);
calendar.set(GregorianCalendar.DAY_OF_MONTH, day);
calendar.set(GregorianCalendar.HOUR_OF_DAY, 0);
calendar.set(GregorianCalendar.MINUTE, 0);
calendar.set(GregorianCalendar.SECOND, 0);
calendar.set(GregorianCalendar.MILLISECOND, 0);
calendar.add(GregorianCalendar.MILLISECOND, millisInDay);
return calendar.getTime();
}
}
2 changes: 1 addition & 1 deletion src/test/java/io/github/persiancalendar/MainTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -74,6 +74,6 @@ public final void test_equinox_time() {
assertEquals(1584676183400L, Equinox.NORTHWARD_EQUINOX.inYear(2020).getTime());
assertEquals(1592689390621L, Equinox.NORTHERN_SOLSTICE.inYear(2020).getTime());
assertEquals(1600781435095L, Equinox.SOUTHWARD_EQUINOX.inYear(2020).getTime());
assertEquals(1608544954756L, Equinox.SOUTHERN_SOLSTICE.inYear(2020).getTime());
assertEquals(1608544954755L, Equinox.SOUTHERN_SOLSTICE.inYear(2020).getTime());
}
}

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