lib/monotone.js
function PartialHull(a, b, idx, lowerIds, upperIds) {
  this.a = a
  this.b = b
  this.idx = idx
  this.lowerIds = lowerIds
  this.upperIds = upperIds
}
function PartialHull(a, b, idx, lowerIds, upperIds) {
  this.a = a
  this.b = b
  this.idx = idx
  this.lowerIds = lowerIds
  this.upperIds = upperIds
}
A partial convex hull fragment, made of two unimonotone polygons