5980be9b3c
This work is based in part on code from NetBSD libm, libc and kernel. The library is partly public domain and partly BSD-style licensed.
125 lines
2.9 KiB
C
125 lines
2.9 KiB
C
/* $NetBSD: cephes_subr.c,v 1.1 2007/08/20 16:01:33 drochner Exp $ */
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/*-
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* Copyright (c) 2007 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software written by Stephen L. Moshier.
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* It is redistributed by the NetBSD Foundation by permission of the author.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "../src/namespace.h"
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#include <complex.h>
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#include <math.h>
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#include "cephes_subr.h"
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/* calculate cosh and sinh */
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void
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_cchsh(double x, double *c, double *s)
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{
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double e, ei;
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if (fabs(x) <= 0.5) {
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*c = cosh(x);
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*s = sinh(x);
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} else {
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e = exp(x);
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ei = 0.5 / e;
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e = 0.5 * e;
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*s = e - ei;
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*c = e + ei;
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}
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}
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/* Program to subtract nearest integer multiple of PI */
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/* extended precision value of PI: */
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static const double DP1 = 3.14159265160560607910E0;
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static const double DP2 = 1.98418714791870343106E-9;
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static const double DP3 = 1.14423774522196636802E-17;
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#define MACHEP 1.1e-16
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double
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_redupi(double x)
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{
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double t;
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long i;
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t = x / M_PI;
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if (t >= 0.0)
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t += 0.5;
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else
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t -= 0.5;
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i = t; /* the multiple */
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t = i;
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t = ((x - t * DP1) - t * DP2) - t * DP3;
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return t;
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}
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/* Taylor series expansion for cosh(2y) - cos(2x) */
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double
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_ctans(double complex z)
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{
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double f, x, x2, y, y2, rn, t;
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double d;
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x = fabs(2.0 * creal(z));
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y = fabs(2.0 * cimag(z));
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x = _redupi(x);
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x = x * x;
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y = y * y;
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x2 = 1.0;
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y2 = 1.0;
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f = 1.0;
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rn = 0.0;
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d = 0.0;
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do {
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rn += 1.0;
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f *= rn;
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rn += 1.0;
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f *= rn;
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x2 *= x;
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y2 *= y;
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t = y2 + x2;
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t /= f;
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d += t;
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rn += 1.0;
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f *= rn;
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rn += 1.0;
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f *= rn;
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x2 *= x;
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y2 *= y;
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t = y2 - x2;
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t /= f;
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d += t;
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} while (fabs(t/d) > MACHEP);
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return d;
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}
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