1#![no_std]
2
3use either::Either;
4
5pub trait Sift<T> {
6 type Residue;
7 fn sift(self) -> Result<T, Self::Residue>;
8 fn of(t: T) -> Self;
9 fn lift(r: Self::Residue) -> Self;
10}
11impl<T, U, A: Sift<T, Residue: Sift<U>>> Sift<Either<T, U>> for A {
12 type Residue = <<A as Sift<T>>::Residue as Sift<U>>::Residue;
13
14 fn sift(self) -> Result<Either<T, U>, Self::Residue> {
15 match self.sift() {
16 Ok(a) => Ok(Either::Left(a)),
17 Err(b) => b.sift().map(Either::Right),
18 }
19 }
20
21 fn of(t: Either<T, U>) -> Self {
22 match t {
23 Either::Left(a) => <A as Sift<T>>::of(a),
24 Either::Right(b) => <A as Sift<T>>::lift(<<A as Sift<T>>::Residue as Sift<U>>::of(b)),
25 }
26 }
27
28 fn lift(r: Self::Residue) -> Self {
29 <A as Sift<T>>::lift(<<A as Sift<T>>::Residue as Sift<U>>::lift(r))
30 }
31}