Macro lambda_calculus::pi

macro_rules! pi {
    ($i:expr, $n:expr) => { ... };
}

A macro for obtaining a projection function (π) providing the i-th (one-indexed) element of a lambda-encoded n-tuple.

Example

use lambda_calculus::term::*;
use lambda_calculus::*;

let t2 = || tuple!(1.into_church(), 2.into_church());

assert_eq!(beta(app(pi!(1, 2), t2()), NOR, 0), 1.into_church());
assert_eq!(beta(app(pi!(2, 2), t2()), NOR, 0), 2.into_church());

let t3 = || tuple!(1.into_church(), 2.into_church(), 3.into_church());

assert_eq!(beta(app(pi!(1, 3), t3()), NOR, 0), 1.into_church());
assert_eq!(beta(app(pi!(2, 3), t3()), NOR, 0), 2.into_church());
assert_eq!(beta(app(pi!(3, 3), t3()), NOR, 0), 3.into_church());