Benjamin Schultzer
40 lines
1003 B
Rust
40 lines
1003 B
Rust
use super::exp;
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use super::expm1;
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use super::k_expo2;
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/// Hyperbolic cosine (f64)
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///
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/// Computes the hyperbolic cosine of the argument x.
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/// Is defined as `(exp(x) + exp(-x))/2`
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/// Angles are specified in radians.
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#[inline]
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#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
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pub fn cosh(mut x: f64) -> f64 {
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/* |x| */
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let mut ix = x.to_bits();
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ix &= 0x7fffffffffffffff;
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x = f64::from_bits(ix);
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let w = ix >> 32;
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/* |x| < log(2) */
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if w < 0x3fe62e42 {
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if w < 0x3ff00000 - (26 << 20) {
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let x1p120 = f64::from_bits(0x4770000000000000);
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force_eval!(x + x1p120);
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return 1.;
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}
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let t = expm1(x); // exponential minus 1
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return 1. + t * t / (2. * (1. + t));
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}
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/* |x| < log(DBL_MAX) */
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if w < 0x40862e42 {
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let t = exp(x);
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/* note: if x>log(0x1p26) then the 1/t is not needed */
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return 0.5 * (t + 1. / t);
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}
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/* |x| > log(DBL_MAX) or nan */
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k_expo2(x)
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}
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