/rust/registry/src/index.crates.io-6f17d22bba15001f/libm-0.2.11/src/math/atanhf.rs
Line | Count | Source (jump to first uncovered line) |
1 | | use super::log1pf; |
2 | | |
3 | | /* atanh(x) = log((1+x)/(1-x))/2 = log1p(2x/(1-x))/2 ~= x + x^3/3 + o(x^5) */ |
4 | | /// Inverse hyperbolic tangent (f32) |
5 | | /// |
6 | | /// Calculates the inverse hyperbolic tangent of `x`. |
7 | | /// Is defined as `log((1+x)/(1-x))/2 = log1p(2x/(1-x))/2`. |
8 | | #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
9 | 0 | pub fn atanhf(mut x: f32) -> f32 { |
10 | 0 | let mut u = x.to_bits(); |
11 | 0 | let sign = (u >> 31) != 0; |
12 | 0 |
|
13 | 0 | /* |x| */ |
14 | 0 | u &= 0x7fffffff; |
15 | 0 | x = f32::from_bits(u); |
16 | 0 |
|
17 | 0 | if u < 0x3f800000 - (1 << 23) { |
18 | 0 | if u < 0x3f800000 - (32 << 23) { |
19 | | /* handle underflow */ |
20 | 0 | if u < (1 << 23) { |
21 | 0 | force_eval!((x * x) as f32); |
22 | 0 | } |
23 | 0 | } else { |
24 | 0 | /* |x| < 0.5, up to 1.7ulp error */ |
25 | 0 | x = 0.5 * log1pf(2.0 * x + 2.0 * x * x / (1.0 - x)); |
26 | 0 | } |
27 | 0 | } else { |
28 | 0 | /* avoid overflow */ |
29 | 0 | x = 0.5 * log1pf(2.0 * (x / (1.0 - x))); |
30 | 0 | } |
31 | | |
32 | 0 | if sign { -x } else { x } |
33 | 0 | } |