rust/tests/ui/try-trait/try-as-monad.rs
2023-01-11 09:32:08 +00:00

25 lines
471 B
Rust

// run-pass
#![feature(try_trait_v2)]
use std::ops::Try;
fn monad_unit<T: Try>(x: <T as Try>::Output) -> T {
T::from_output(x)
}
fn monad_bind<T1: Try<Residual = R>, T2: Try<Residual = R>, R>(
mx: T1,
f: impl FnOnce(<T1 as Try>::Output) -> T2)
-> T2 {
let x = mx?;
f(x)
}
fn main() {
let mx: Option<i32> = monad_unit(1);
let my = monad_bind(mx, |x| Some(x + 1));
let mz = monad_bind(my, |x| Some(-x));
assert_eq!(mz, Some(-2));
}