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#include "libm.h" // for ldshape, ldshape::(anonymous), FORCE_EVAL
#include <float.h> // for LDBL_MANT_DIG, LDBL_MAX_EXP
#include <math.h> // for log1pl, atanhl
#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
long double atanhl(long double x)
{
return atanh(x);
}
#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)
{
union ldshape u = { x };
unsigned e = u.i.se & 0x7fff;
unsigned s = u.i.se >> 15;
/* |x| */
u.i.se = e;
x = u.f;
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 {
/* avoid overflow */
x = 0.5 * log1pl(2 * (x / (1 - x)));
}
return s ? -x : x;
}
#endif
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