immutable array methods

const clone = (x) => [...x]

const push = (y) => (x) => [...x, y]

const pop = (x) => x.slice(0, -1)

const unshift = (y) => (x) => [y, ...x]

const shift = (x) => x.slice(1)

const sort = (fn) => (x) => x.sort(fn)

const delete = (i) => (x) => [...x.slice(0, i), ...x.slice(i + 1)]

const splice = (s, c, ...y) => x => [...x.slice(0, s), ...y, ...x.slice(s+c)]