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88 lines
3.2 KiB
C
88 lines
3.2 KiB
C
/*
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* calcsin.c
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*
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* Copyright 2016 Edward V. Emelianov <eddy@sao.ru, edward.emelianoff@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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* MA 02110-1301, USA.
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*/
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#include <stdio.h>
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#include <math.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <limits.h>
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#define ONE_FIXPT (10000)
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#define SZ (61)
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typedef int32_t TYPE;
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#define _PI (31415)
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#define _2PI (62831)
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#define _PI_2 (15707)
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TYPE angles[61] = {0, 966, 1700, 2025, 2331, 2622, 2898, 3163, 3418, 3663, 3900, 4129, 4351, 4566, 4982, 5375, 5747, 6102, 6441, 6764, 7073, 7369, 7652, 7925, 8186, 8438, 8680, 8912, 9136, 9352, 9560, 9761, 9954, 10141, 10321, 10495, 10663, 10825, 10982, 11133, 11425, 11698, 11953, 12191, 12414, 12622, 12817, 12999, 13170, 13329, 13479, 13759, 14003, 14217, 14404, 14567, 14710, 14959, 15147, 15427, 15708};
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TYPE sinuses[61] = {0, 965, 1692, 2011, 2310, 2592, 2858, 3111, 3352, 3582, 3802, 4013, 4215, 4409, 4778, 5119, 5436, 5731, 6004, 6260, 6498, 6720, 6927, 7121, 7302, 7472, 7630, 7778, 7917, 8047, 8169, 8283, 8390, 8490, 8584, 8672, 8754, 8831, 8904, 8972, 9097, 9207, 9303, 9388, 9462, 9528, 9585, 9635, 9680, 9718, 9753, 9811, 9855, 9889, 9915, 9935, 9950, 9972, 9984, 9996, 10000};
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TYPE calcsin(TYPE rad){
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rad %= _2PI;
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if(rad < 0) rad += _2PI;
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TYPE sign = 1;
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if(rad > _PI){
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rad -= _PI;
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sign = -1;
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}
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if(rad > _PI_2) rad = _PI - rad;
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// find interval for given angle
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int ind = 0, half = SZ/2, end = SZ - 1, iter=0;
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do{
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++iter;
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if(angles[half] > rad){ // left half
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end = half;
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}else{ // right half
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ind = half;
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}
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half = ind + (end - ind) / 2;
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}while(angles[ind] > rad || angles[ind+1] < rad);
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//printf("%d iterations, ind=%d, ang[ind]=%d, ang[ind+1]=%d\n", iter, ind, angles[ind], angles[ind+1]);
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TYPE ai = angles[ind], si = sinuses[ind];
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if(ai == rad) return si;
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++ind;
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if(angles[ind] == rad) return sinuses[ind];
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return sign*(si + (sinuses[ind] - si)*(rad - ai)/(angles[ind] - ai));
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}
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TYPE calccos(TYPE rad){
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return calcsin(_PI_2 - rad);
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}
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TYPE calctan(TYPE rad){
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TYPE s = calcsin(rad) * ONE_FIXPT, c = calccos(rad);
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if(c) return s/calccos(rad);
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else return INT_MAX;
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}
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int main(int argc, char **argv){
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if(argc != 2) return 1;
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double ang = strtod(argv[1], NULL), drad = ang * M_PI/180.;
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//printf("rad: %g\n", drad);
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TYPE rad = (TYPE)(drad * ONE_FIXPT);
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printf("Approximate sin of %g (%d) = %g, exact = %g\n",
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drad, rad, calcsin(rad)/((double)ONE_FIXPT), sin(drad));
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printf("Approximate cos of %g (%d) = %g, exact = %g\n",
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drad, rad, calccos(rad)/((double)ONE_FIXPT), cos(drad));
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printf("Approximate tan of %g (%d) = %g, exact = %g\n",
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drad, rad, calctan(rad)/((double)ONE_FIXPT), tan(drad));
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return 0;
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}
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