100 lines
1.7 KiB
C
Executable File
100 lines
1.7 KiB
C
Executable File
/*
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* (c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
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* See the copyright notice in the ACK home directory, in the file "Copyright".
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*
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* Author: Ceriel J.H. Jacobs
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*/
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/* $Header$ */
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#include <math.h>
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#include <float.h>
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#include <errno.h>
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#include "localmath.h"
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static double
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sinus(double x, int cos_flag)
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{
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/* Algorithm and coefficients from:
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"Software manual for the elementary functions"
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by W.J. Cody and W. Waite, Prentice-Hall, 1980
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*/
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static double r[] = {
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-0.16666666666666665052e+0,
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0.83333333333331650314e-2,
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-0.19841269841201840457e-3,
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0.27557319210152756119e-5,
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-0.25052106798274584544e-7,
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0.16058936490371589114e-9,
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-0.76429178068910467734e-12,
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0.27204790957888846175e-14
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};
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double y;
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int neg = 1;
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if (__IsNan(x)) {
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errno = EDOM;
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return x;
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}
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if (x < 0) {
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x = -x;
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neg = -1;
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}
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if (cos_flag) {
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neg = 1;
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y = M_PI_2 + x;
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}
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else y = x;
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/* ??? avoid loss of significance, if y is too large, error ??? */
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y = y * M_1_PI + 0.5;
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if (y >= DBL_MAX/M_PI) return 0.0;
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/* Use extended precision to calculate reduced argument.
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Here we used 12 bits of the mantissa for a1.
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Also split x in integer part x1 and fraction part x2.
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*/
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#define A1 3.1416015625
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#define A2 -8.908910206761537356617e-6
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{
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double x1, x2;
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modf(y, &y);
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if (modf(0.5*y, &x1)) neg = -neg;
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if (cos_flag) y -= 0.5;
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x2 = modf(x, &x1);
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x = x1 - y * A1;
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x += x2;
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x -= y * A2;
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#undef A1
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#undef A2
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}
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if (x < 0) {
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neg = -neg;
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x = -x;
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}
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/* ??? avoid underflow ??? */
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y = x * x;
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x += x * y * POLYNOM7(y, r);
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return neg==-1 ? -x : x;
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}
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double
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sin(double x)
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{
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return sinus(x, 0);
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}
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double
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cos(double x)
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{
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if (x < 0) x = -x;
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return sinus(x, 1);
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}
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