Church Numerals JavaScript

church-numerals.js

// Implementation independant

const Z =
  (inc) => (zero) => zero;

const S =
  (n_times) =>
    (inc) => (zero) => inc(n_times(inc)(zero));

const add2 =
  (m_times) => (n_times) =>
    (inc) => (zero) => m_times(inc)(n_times(inc)(zero));

const add3 =
  (x) => (y) => (z) => add2(x)(add2(y)(z));

const one = S(Z);
const two = S(one);
const three = S(two);

const one_plus_two_plus_three = add3(one)(two)(three);

// Implementation for numbers

const number_zero = 0;
const number_inc = (x) => x + 1;
const to_number = (n) => n(number_inc)(number_zero);
console.log(to_number(one_plus_two_plus_three));

// Implementation for asterisks

const asterisk_zero = "";
const asterisk_inc = (x) => x + "*";
const to_asterisk = (n) => n(asterisk_inc)(asterisk_zero);
console.log(to_asterisk(one_plus_two_plus_three));

See here for discussion: https://langdev.stackexchange.com/q/3228/2116