Function batch_oper::using

pub fn using<T, R>(v: T, f: impl FnOnce(T) -> R) -> R

Create an implicit variable, and make a mapping for it

Example

let v = 1;
let mut v = using(v, |v| { v + 1 });
assert_eq!(v, 2);
using(&mut v, |v| { *v = 3 });
assert_eq!(v, 3);