code: function (/*Point*/ p, /*Point*/ p1, /*Point*/ p2, /*Point*/ p3) {
  		return	this._checkCounterclockwise(p, p2, p3) !==
  				this._checkCounterclockwise(p1, p2, p3) &&
  				this._checkCounterclockwise(p, p1, p2) !==
  				this._checkCounterclockwise(p, p1, p3);
  	}
docs: Checks to see if two line segments intersect. Does not handle degenerate cases. http://compgeom.cs.uiuc.edu/~jeffe/teaching/373/notes/x06-sweepline.pdf