82 lines
1.4 KiB
C
82 lines
1.4 KiB
C
/*
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* (c) copyright 1989 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 <errno.h>
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extern int errno;
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extern double exp();
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static double
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sinh_cosh(x, cosh_flag)
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double x;
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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 p[] = {
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-0.35181283430177117881e+6,
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-0.11563521196851768270e+5,
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-0.16375798202630751372e+3,
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-0.78966127417357099479e+0
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};
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static double q[] = {
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-0.21108770058106271242e+7,
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0.36162723109421836460e+5,
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-0.27773523119650701167e+3,
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1.0
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};
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int negative = x < 0;
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double y = negative ? -x : x;
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if (! cosh_flag && y <= 1.0) {
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/* ??? check for underflow ??? */
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y = y * y;
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return x + x * y * POLYNOM3(y, p)/POLYNOM3(y,q);
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}
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if (y >= M_LN_MAX_D) {
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/* exp(y) would cause overflow */
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#define LNV 0.69316101074218750000e+0
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#define VD2M1 0.52820835025874852469e-4
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double w = y - LNV;
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if (w < M_LN_MAX_D+M_LN2-LNV) {
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x = exp(w);
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x += VD2M1 * x;
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}
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else {
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errno = ERANGE;
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x = HUGE;
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}
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}
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else {
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double z = exp(y);
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x = 0.5 * (z + (cosh_flag ? 1.0 : -1.0)/z);
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}
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return negative ? -x : x;
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}
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double
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sinh(x)
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double x;
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{
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return sinh_cosh(x, 0);
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}
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double
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cosh(x)
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double x;
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{
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if (x < 0) x = -x;
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return sinh_cosh(x, 1);
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}
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