lamda-calculus-es6.js

// This is the implmenetation of some of the lamdas from lamda calculus
// https://en.wikipedia.org/wiki/Lambda_calculus
console.clear();

const log = function(x) {
  console.log('log: ' + x);
  return x;
}

// Boolean:

const T     = t => f => t
const F     = t => f => f

const IF    = P => x => y => P(x)(y)
const OR    = x => y => IF(T)(x)(y)
const AND   = x => y => IF(F)(x)(y)

// Church numbers

const SUCC  = n => f => x => f(n(f)(x))

const _0    = f => x => x
const _1    = SUCC(_0) // f(x)        === f(_0)
const _2    = SUCC(_1) // f(f(x))     === f(_1)
const _3    = SUCC(_2) // f(f(f(x)))  === f(_2)
const _4    = SUCC(_3) // ...
const _5    = SUCC(_4)
const _6    = SUCC(_5)

_5(log)('123123')

const IsZero = n => n(x=>F)(T)

console.log( 'IsZero: ' + IsZero(_0)(1)(0) );
console.log( 'IF.IsZero: ' + IF(IsZero(_0))(1)(0) );

// Data structures
const PAIR = x => y => f => f(x)(y)
const NIL = x => T
const FST = p => p(x => y => x)
const SND = p => p(x => y => y)
const NULL = p => p( x => y => F )

let pair = PAIR(1)(2);
console.log( 'FST: ' + FST(pair) );
console.log( 'SND: ' + SND(pair) );

console.log( NULL(NIL)('Y')('N') );

let list = PAIR(3)(PAIR(2)(PAIR(1)(NIL)))
console.log( NULL(list)('Y')('N') )