clip_array.js

// usefull object, to clip array in O(1) when we don't want to make copies of it (slice)

const ClipArray = arr => {
  let low = 0;
  let up = arr.length;
  const length = () => up - low;
  return {
    clipHead: n => {
      low += n;
      if (low > up) low = up;
    },
    clipTail: n => {
      up -= n;
      if (up < low) up = low;
    },
    get: idx => {
			if (idx >= length || idx < 0) return [][0];
      return arr[low + idx];
    },
    getClipped: () => arr.slice(low, up),
		length
  };
};