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;
13 if (u.i < 0x3f800000 - (1<<23)) {
14 /* |x| < 0.5, up to 1.7ulp error */
15 x = 0.5f*log1pf(2*x + 2*x*x/(1-x));
17 x = 0.5f*log1pf(2*x/(1-x));