minix/lib/math/sinh.c
2009-11-09 10:26:00 +00:00

81 lines
1.5 KiB
C

/*
* (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
*/
/* $Header$ */
#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);
}