libm/math/
cosh.rs

1use super::exp;
2use super::expm1;
3use super::k_expo2;
4
5/// Hyperbolic cosine (f64)
6///
7/// Computes the hyperbolic cosine of the argument x.
8/// Is defined as `(exp(x) + exp(-x))/2`
9/// Angles are specified in radians.
10#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
11pub fn cosh(mut x: f64) -> f64 {
12    /* |x| */
13    let mut ix = x.to_bits();
14    ix &= 0x7fffffffffffffff;
15    x = f64::from_bits(ix);
16    let w = ix >> 32;
17
18    /* |x| < log(2) */
19    if w < 0x3fe62e42 {
20        if w < 0x3ff00000 - (26 << 20) {
21            let x1p120 = f64::from_bits(0x4770000000000000);
22            force_eval!(x + x1p120);
23            return 1.;
24        }
25        let t = expm1(x); // exponential minus 1
26        return 1. + t * t / (2. * (1. + t));
27    }
28
29    /* |x| < log(DBL_MAX) */
30    if w < 0x40862e42 {
31        let t = exp(x);
32        /* note: if x>log(0x1p26) then the 1/t is not needed */
33        return 0.5 * (t + 1. / t);
34    }
35
36    /* |x| > log(DBL_MAX) or nan */
37    k_expo2(x)
38}