Using Ramda, and pointfree style, how can I copy the first item of an array to the end of it?

Question

I want to take an array [1, 2, 3] and return [1, 2, 3, 1].

I\'m using Ramda, and I can get the desired result like this:

const          


        

Answer 1

The S combinator is useful here:

S.S(S.C(R.append), R.head, [1, 2, 3]);
// => [1, 2, 3, 1]

Answer 2

converge can be very helpful for things like this.

const rotate = R.converge(R.append, [R.head, R.identity])
rotate([1, 2, 3]); //=> [1, 2, 3, 1]