comb.js

// Combinators
const I = x => x
const K = (x, y) => x
const S = (b, u) => x => b(u(x), x)
const Sp = (b, u, v) => x => b(u(x), v(x))
const B = (u, v) => (x) => u(v(x))
const C = (b, u, v) => (x, y) => b(u(x, y), v(y))

// Helpers
const eq = (x, y) => x === y
const reverse = (s) => s.split("").reverse().join("")
const flip = f => (x, y) => f(y, x)
const max = xs => xs.sort()[xs.length - 1]
const min = xs => xs.sort()[0]
const pair = (x, y) => [x, y]
const partition_aux = (carr, parr, aux) => {
    if (carr.length === 0 || parr.length === 0) return aux

    return partition_aux(
        carr.slice(1),
        parr.slice(1),
        (carr[0] === 0) ? [[...aux[0], parr[0]], aux[1]] : [aux[0], [...aux[1], parr[0]]]
    )
}
const partition = (carr, parr) => partition_aux(carr, parr, [[], []])
const same_aux = (xs, ys, comp) => {
    if (xs.length === 0 || ys.length === 0) return comp

    return same_aux(xs.slice(1), ys.slice(1), [...comp, (xs[0] === ys[0])? 1 : 0])
}
const same_arr = (xs, ys) => same_aux(xs, ys, [])

// Applications
const isPalindrome1 = S(eq, reverse) 
const isPalindrome2 = Sp(eq, reverse, I)
const minMaxPair = Sp(pair, min, max)