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- /*
- * (c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
- * See the copyright notice in the ACK home directory, in the file "Copyright".
- *
- * Author: Ceriel J.H. Jacobs
- */
- /* $Id$ */
- #include <math.h>
- #include <float.h>
- #include <errno.h>
- #include "localmath.h"
- static double
- sinh_cosh(double x, int cosh_flag)
- {
- /* Algorithm and coefficients from:
- "Software manual for the elementary functions"
- by W.J. Cody and W. Waite, Prentice-Hall, 1980
- */
- static double p[] = {
- -0.35181283430177117881e+6,
- -0.11563521196851768270e+5,
- -0.16375798202630751372e+3,
- -0.78966127417357099479e+0
- };
- static double q[] = {
- -0.21108770058106271242e+7,
- 0.36162723109421836460e+5,
- -0.27773523119650701167e+3,
- 1.0
- };
- int negative = x < 0;
- double y = negative ? -x : x;
- if (__IsNan(x)) {
- errno = EDOM;
- return x;
- }
- if (! cosh_flag && y <= 1.0) {
- /* ??? check for underflow ??? */
- y = y * y;
- return x + x * y * POLYNOM3(y, p)/POLYNOM3(y,q);
- }
- if (y >= M_LN_MAX_D) {
- /* exp(y) would cause overflow */
- #define LNV 0.69316101074218750000e+0
- #define VD2M1 0.52820835025874852469e-4
- double w = y - LNV;
-
- if (w < M_LN_MAX_D+M_LN2-LNV) {
- x = exp(w);
- x += VD2M1 * x;
- }
- else {
- errno = ERANGE;
- x = HUGE_VAL;
- }
- }
- else {
- double z = exp(y);
-
- x = 0.5 * (z + (cosh_flag ? 1.0 : -1.0)/z);
- }
- return negative ? -x : x;
- }
- double
- sinh(double x)
- {
- return sinh_cosh(x, 0);
- }
- double
- cosh(double x)
- {
- if (x < 0) x = -x;
- return sinh_cosh(x, 1);
- }
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