28 lines
438 B
C
28 lines
438 B
C
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/*
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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 <math.h>
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#include <errno.h>
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double
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tanh(x)
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double x;
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{
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extern double exp();
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if (x <= 0.5*M_LN_MIN_D) {
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return -1;
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}
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if (x >= 0.5*M_LN_MAX_D) {
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return 1;
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}
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x = exp(x + x);
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return (x - 1.0)/(x + 1.0);
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}
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