edgequad = function() {
    this._geom = _geom;
    this._tree = null;
    this._cache = {
      query: false,
      result: false
    };
    this._enabled = true;
  }
The edgequad core that will become the sigma interface with the quadtree.

property {object} _tree     Property holding the quadtree object.
property {object} _geom     Exposition of the _geom namespace for testing.
property {object} _cache    Cache for the area method.
property {boolean} _enabled Can index and retreive elements.