Function lambda_calculus::data::option::unwrap_or

pub fn unwrap_or() -> Term

Applied to one argument and a lambda-encoded option it returns the value inside the option or the first argument if the option doesn’t contain a value.

UNWRAP_OR ≡ λdm.m d I ≡ λ λ 1 2 I

Example

use lambda_calculus::data::option::{unwrap_or, none};
use lambda_calculus::*;

let some_one: Term = Some(1).into_church();

assert_eq!(beta(app!(unwrap_or(), 2.into_church(), some_one), NOR, 0), 1.into_church());
assert_eq!(beta(app!(unwrap_or(), 2.into_church(), none()), NOR, 0), 2.into_church());