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/* $OpenBSD: pesach.c,v 1.4 2015/03/15 00:41:28 millert Exp $ */ |
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/* |
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* Copyright (c) 2004 Michael Shalayeff |
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* All rights reserved. |
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* |
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* Permission to use, copy, modify, and distribute this software for any |
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* purpose with or without fee is hereby granted, provided that the above |
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* copyright notice and this permission notice appear in all copies. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR |
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
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* WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER IN |
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* AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT |
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* OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
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*/ |
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#include <stdio.h> |
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#include "calendar.h" |
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/* Calculate the Julian date of Pesach using the Gauss formula */ |
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#define T (33. + 14. / 24.) |
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#define L ((1. + 485. / 1080.) / 24. / 19.) |
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#define K ((29. + (12. + 793. / 1080.) / 24. ) / 19.) |
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int |
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pesach(int R) |
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{ |
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int a, b, y, cumdays; |
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double d; |
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y = R + 3760; |
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a = (12 * y + 17) % 19; |
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b = y % 4; |
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d = (T - 10 * K + L + 14) + K * a + b / 4. - L * y; |
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cumdays = d; |
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/* the postponement */ |
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switch ((int)(cumdays + 3 * y + 5 * b + 5) % 7) { |
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case 1: |
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if (a > 6 && d - cumdays >= (15. + 204. / 1080.) / 24.) |
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cumdays += 2; |
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break; |
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case 0: |
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if (a <= 11 || d - cumdays < (21. + 589. / 1080.) / 24.) |
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break; |
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/* FALLTHROUGH */ |
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case 2: |
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case 4: |
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case 6: |
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cumdays++; |
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break; |
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} |
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if (R > 1582) |
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cumdays += R / 100 - R /400 - 2; |
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return (31 + 28 + cumdays + (isleap(R)? 1 : 0)); |
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} |