{
return atanh(x);
}
-#elif LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
+#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
/* atanh(x) = log((1+x)/(1-x))/2 = log1p(2x/(1-x))/2 ~= x + x^3/3 + o(x^5) */
long double atanhl(long double x)
{
u.i.se = e;
x = u.f;
- if (e < 0x3fff - 1) {
- /* |x| < 0.5, up to 1.7ulp error */
- x = 0.5*log1pl(2*x + 2*x*x/(1-x));
+ if (e < 0x3ff - 1) {
+ if (e < 0x3ff - LDBL_MANT_DIG/2) {
+ /* handle underflow */
+ if (e == 0)
+ FORCE_EVAL((float)x);
+ } else {
+ /* |x| < 0.5, up to 1.7ulp error */
+ x = 0.5*log1pl(2*x + 2*x*x/(1-x));
+ }
} else {
- x = 0.5*log1pl(2*x/(1-x));
+ /* avoid overflow */
+ x = 0.5*log1pl(2*(x/(1-x)));
}
return s ? -x : x;
}