3 /* atanh(x) = log((1+x)/(1-x))/2 = log1p(2x/(1-x))/2 ~= x + x^3/3 + o(x^5) */
6 union {float f
; uint32_t i
;} u
= {.f
= x
};
7 unsigned s
= u
.i
>> 31;
14 if (u
.i
< 0x3f800000 - (1<<23)) {
15 if (u
.i
< 0x3f800000 - (32<<23)) {
16 /* handle underflow */
18 FORCE_EVAL((float)(y
*y
));
20 /* |x| < 0.5, up to 1.7ulp error */
21 y
= 0.5f
*log1pf(2*y
+ 2*y
*y
/(1-y
));
25 y
= 0.5f
*log1pf(2*(y
/(1-y
)));