/usr/share/sdcc/lib/src/tanhf.c is in sdcc-libraries 2.9.0-5.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | /* tanhf.c: Computes tanh(x) where x is a 32-bit float as outlined in [1].
Copyright (C) 2001, 2002 Jesus Calvino-Fraga, jesusc@ieee.org
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/* [1] William James Cody and W. M. Waite. _Software manual for the
elementary functions_, Englewood Cliffs, N.J.:Prentice-Hall, 1980. */
/* Version 1.0 - Initial release */
#include <math.h>
#include <errno.h>
#define P0 -0.8237728127E+0
#define P1 -0.3831010665E-2
#define Q0 0.2471319654E+1
#define Q1 0.1000000000E+1
/* ln(3)/2 */
#define K1 0.5493061443E+0
/* SBIG=[ln(2)+(t+1)*ln(B)]/2 */
#define SBIG 9.01091
#define P(g) ((P1*g+P0)*g)
#define Q(g) (Q1*g+Q0)
float tanhf(const float x) _FLOAT_FUNC_REENTRANT
{
float f, g, r;
f=fabsf(x);
if(f>SBIG) r=1.0;
else if(f>K1)
{
r=0.5-1.0/(expf(f+f)+1.0);
r+=r;
}
else if(f<EPS) r=f;
else
{
g=f*f;
r=f+f*(P(g)/Q(g));
}
if(x<0.0) r=-r;
return r;
}
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