1 use super::exp;
2 use super::expm1;
3 use 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)]
cosh(mut x: f64) -> f6411 pub 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