Mercurial > mxe-octave
diff 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> |
|---|---|
| date | Mon, 17 Jun 2013 22:43:11 -0400 |
| parents | |
| children |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/build-msvctools/math/atanh.c Mon Jun 17 22:43:11 2013 -0400 @@ -0,0 +1,31 @@ +#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; +}