Function sub_rrule 

pub fn sub_rrule<S: ScalarAd>(cotangent: S) -> (S, S)

Reverse rule for sub.

Returns cotangents with respect to (x, y).

Examples

use chainrules::sub_rrule;

let (dx, dy) = sub_rrule(2.0_f64);
assert_eq!(dx, 2.0_f64);
assert_eq!(dy, -2.0_f64);