code: function reflexLeft(left, p, i0, i1) {
      for(var i=i1; i>i0; --i) {
        var a = left[i-1]
        var b = left[i]
        if(orient(a, b, p) <= 0) {
          cells.push([a[2], b[2], p[2]])
        } else {
          return i
        }
      }
      return i0
    }
docs: Remove all left reflex vertices starting from p