From 8c1ab65c0f548d20b7f177bdb736daaf603340e1 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 15:54:38 +0200 Subject: Adding upstream version 0.0~git20221206.8b7148f. Signed-off-by: Daniel Baumann --- libc-top-half/musl/src/math/atanh.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) create mode 100644 libc-top-half/musl/src/math/atanh.c (limited to 'libc-top-half/musl/src/math/atanh.c') diff --git a/libc-top-half/musl/src/math/atanh.c b/libc-top-half/musl/src/math/atanh.c new file mode 100644 index 0000000..63a035d --- /dev/null +++ b/libc-top-half/musl/src/math/atanh.c @@ -0,0 +1,29 @@ +#include "libm.h" + +/* atanh(x) = log((1+x)/(1-x))/2 = log1p(2x/(1-x))/2 ~= x + x^3/3 + o(x^5) */ +double atanh(double x) +{ + union {double f; uint64_t i;} u = {.f = x}; + unsigned e = u.i >> 52 & 0x7ff; + unsigned s = u.i >> 63; + double_t y; + + /* |x| */ + u.i &= (uint64_t)-1/2; + y = u.f; + + if (e < 0x3ff - 1) { + if (e < 0x3ff - 32) { + /* handle underflow */ + if (e == 0) + FORCE_EVAL((float)y); + } else { + /* |x| < 0.5, up to 1.7ulp error */ + y = 0.5*log1p(2*y + 2*y*y/(1-y)); + } + } else { + /* avoid overflow */ + y = 0.5*log1p(2*(y/(1-y))); + } + return s ? -y : y; +} -- cgit v1.2.3