Function sech_frule 

pub fn sech_frule<S: ScalarAd>(x: S, dx: S) -> (S, S)

Forward rule for sech.

Examples

use chainrules::sech_frule;

let (_, dy) = sech_frule(0.5_f64, 1.0);
let sech_x = 1.0 / 0.5_f64.cosh();
assert!((dy + sech_x * 0.5_f64.tanh()).abs() < 1e-12);