1 use super::{log1pf, logf, sqrtf};
2 
3 const LN2: f32 = 0.693147180559945309417232121458176568;
4 
5 /// Inverse hyperbolic cosine (f32)
6 ///
7 /// Calculates the inverse hyperbolic cosine of `x`.
8 /// Is defined as `log(x + sqrt(x*x-1))`.
9 /// `x` must be a number greater than or equal to 1.
10 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
acoshf(x: f32) -> f3211 pub fn acoshf(x: f32) -> f32 {
12     let u = x.to_bits();
13     let a = u & 0x7fffffff;
14 
15     if a < 0x3f800000 + (1 << 23) {
16         /* |x| < 2, invalid if x < 1 or nan */
17         /* up to 2ulp error in [1,1.125] */
18         return log1pf(x - 1.0 + sqrtf((x - 1.0) * (x - 1.0) + 2.0 * (x - 1.0)));
19     }
20     if a < 0x3f800000 + (12 << 23) {
21         /* |x| < 0x1p12 */
22         return logf(2.0 * x - 1.0 / (x + sqrtf(x * x - 1.0)));
23     }
24     /* x >= 0x1p12 */
25     return logf(x) + LN2;
26 }
27