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}
39