Mercurial > mxe-octave
view src/build-msvctools/math/atanh.c @ 3061:f8299bb6c872
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> |
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date | Mon, 17 Jun 2013 22:43:11 -0400 |
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#include <math.h> #include <errno.h> #include "fastmath.h" /* atanh (x) = 0.5 * log ((1.0 + x)/(1.0 - x)) */ double atanh(double x) { double z; if isnan (x) return x; z = fabs (x); if (z == 1.0) { errno = ERANGE; return (x > 0 ? INFINITY : -INFINITY); } if (z > 1.0) { errno = EDOM; return nan(""); } /* Rearrange formula to avoid precision loss for small x. atanh(x) = 0.5 * log ((1.0 + x)/(1.0 - x)) = 0.5 * log1p ((1.0 + x)/(1.0 - x) - 1.0) = 0.5 * log1p ((1.0 + x - 1.0 + x) /(1.0 - x)) = 0.5 * log1p ((2.0 * x ) / (1.0 - x)) */ z = 0.5 * __fast_log1p ((z + z) / (1.0 - z)); return x >= 0 ? z : -z; }