34 lines
588 B
C
34 lines
588 B
C
/*
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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 <errno.h>
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#include <math.h>
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#include "localmath.h"
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double
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cosh(double x)
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{
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if (x < 0) {
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x = -x;
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}
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if (x > M_LN_MAX_D) {
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/* exp(x) would overflow */
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if (x >= M_LN_MAX_D + M_LN2) {
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/* not representable */
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x = HUGE_VAL;
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errno = ERANGE;
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}
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else x = exp (x - M_LN2);
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}
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else {
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double expx = exp(x);
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x = 0.5 * (expx + 1.0/expx);
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}
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return x;
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}
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