Function sign_frule 

pub fn sign_frule<R: Float>(x: R, _dx: R) -> (R, R)

Forward rule for sign.

The tangent is always zero.

Examples

use chainrules::sign_frule;

let (y, dy) = sign_frule(-2.0_f64, 0.75);
assert_eq!(y, -1.0);
assert_eq!(dy, 0.0);