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comparison src/build-msvctools/math/atanhf.c @ 3061:f8299bb6c872

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Initial support for native MSVC compilation. * add MSVC support files: compiler wrappers and support libraries * adapt libiconv to work with MSVC * adapt gettext to work with MSVC
author Michael Goffioul <michael.goffioul@gmail.com>
date Mon, 17 Jun 2013 22:43:11 -0400
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3060:cbdf4575016d 3061:f8299bb6c872
1 #include <math.h>
2 #include <errno.h>
3 #include "fastmath.h"
4
5 /* atanh (x) = 0.5 * log ((1.0 + x)/(1.0 - x)) */
6 float atanhf (float x)
7 {
8 float z;
9 if isnan (x)
10 return x;
11 z = fabsf (x);
12 if (z == 1.0)
13 {
14 errno = ERANGE;
15 return (x > 0 ? INFINITY : -INFINITY);
16 }
17 if ( z > 1.0)
18 {
19 errno = EDOM;
20 return nanf("");
21 }
22 /* Rearrange formula to avoid precision loss for small x.
23
24 atanh(x) = 0.5 * log ((1.0 + x)/(1.0 - x))
25 = 0.5 * log1p ((1.0 + x)/(1.0 - x) - 1.0)
26 = 0.5 * log1p ((1.0 + x - 1.0 + x) /(1.0 - x))
27 = 0.5 * log1p ((2.0 * x ) / (1.0 - x)) */
28 z = 0.5 * __fast_log1p ((z + z) / (1.0 - z));
29 return x >= 0 ? z : -z;
30 }