function splitCubic(pts/* , ratio */) {
    var t = /* ratio || */ 0.5;
    var p0 = pts.slice(0, 2);
    var p1 = pts.slice(2, 4);
    var p2 = pts.slice(4, 6);
    var p3 = pts.slice(6, 8);
    var p4 = midPoint(p0, p1, t);
    var p5 = midPoint(p1, p2, t);
    var p6 = midPoint(p2, p3, t);
    var p7 = midPoint(p4, p5, t);
    var p8 = midPoint(p5, p6, t);
    var p9 = midPoint(p7, p8, t);

    return [
      ['C' ].concat( p4, p7, p9),
      ['C' ].concat( p8, p6, p3) ];
  }
Split a cubic-bezier segment into two.

@param {number[]} pts the cubic-bezier parameters
@return {SVGPath.cubicSegment[]} two new cubic-bezier segments