libm/math/
tanhf.rs

1use super::expm1f;
2
3/// The hyperbolic tangent of `x` (f32).
4///
5/// `x` is specified in radians.
6#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
7pub fn tanhf(mut x: f32) -> f32 {
8    /* x = |x| */
9    let mut ix = x.to_bits();
10    let sign = (ix >> 31) != 0;
11    ix &= 0x7fffffff;
12    x = f32::from_bits(ix);
13    let w = ix;
14
15    let tt = if w > 0x3f0c9f54 {
16        /* |x| > log(3)/2 ~= 0.5493 or nan */
17        if w > 0x41200000 {
18            /* |x| > 10 */
19            1. + 0. / x
20        } else {
21            let t = expm1f(2. * x);
22            1. - 2. / (t + 2.)
23        }
24    } else if w > 0x3e82c578 {
25        /* |x| > log(5/3)/2 ~= 0.2554 */
26        let t = expm1f(2. * x);
27        t / (t + 2.)
28    } else if w >= 0x00800000 {
29        /* |x| >= 0x1p-126 */
30        let t = expm1f(-2. * x);
31        -t / (t + 2.)
32    } else {
33        /* |x| is subnormal */
34        force_eval!(x * x);
35        x
36    };
37    if sign { -tt } else { tt }
38}