use super::{expf, expm1f, k_expo2f};

/// Hyperbolic cosine (f64)

///

/// Computes the hyperbolic cosine of the argument x.

/// Is defined as `(exp(x) + exp(-x))/2`

/// Angles are specified in radians.

#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]

pub fn coshf(mut x: f32) -> f32 {

    let x1p120 = f32::from_bits(0x7b800000); // 0x1p120f === 2 ^ 120

    /* |x| */

    let mut ix = x.to_bits();

    ix &= 0x7fffffff;

    x = f32::from_bits(ix);

    let w = ix;

    /* |x| < log(2) */

    if w < 0x3f317217 {

        if w < (0x3f800000 - (12 << 23)) {

            force_eval!(x + x1p120);

            return 1.;

        }

        let t = expm1f(x);

        return 1. + t * t / (2. * (1. + t));

    }

    /* |x| < log(FLT_MAX) */

    if w < 0x42b17217 {

        let t = expf(x);

        return 0.5 * (t + 1. / t);

    }

    /* |x| > log(FLT_MAX) or nan */

    k_expo2f(x)

}