Function is_zero 

pub fn is_zero() -> Term

Applied to a Parigot-encoded number it produces a lambda-encoded boolean, indicating whether its argument is equal to zero.

IS_ZERO ≡ λn.n (λxy.FALSE) TRUE ≡ λ 1 (λ λ FALSE) TRUE

Example

use lambda_calculus::data::num::parigot::is_zero;
use lambda_calculus::*;

assert_eq!(beta(app(is_zero(), 0.into_parigot()), NOR, 0), true.into());
assert_eq!(beta(app(is_zero(), 1.into_parigot()), NOR, 0), false.into());