Function lambda_calculus::data::list::pair::index

pub fn index() -> Term

Applied to a Church-encoded number i and a pair-encoded list it returns the i-th (zero-indexed) element of the list.

INDEX ≡ λil.HEAD (i TAIL l) ≡ λ λ HEAD (2 TAIL 1)

Example

use lambda_calculus::data::list::pair::index;
use lambda_calculus::*;

let list = vec![1.into_church(), 2.into_church(), 3.into_church()];

assert_eq!(
    beta(app!(index(), 0.into_church(), list.into_pair_list()), NOR, 0),
    1.into_church()
);