This library is still in the early stages. Expect the interface to change.

TODO:
    - rename Boundary data type 
    - rename HasBoundary type class.
    - query should accept any suitable region. 
        - At least any axis aligned boxes not just square ones
    - partition query into two forms:
        - inclusive: Any element with bounds entirely within or partially the query bounds.
        - exclusive: Any element with bounds entirely within the query bounds.
    - Improve verification tests 
        - Test for proper distribution of inserted elements to nodes.
    - Improve visualization tool
        - interactive querying
        - interactive insert
        - remove FBO dependency.

    Optimization:
        - The following element_bounds_query_is_element_prop instance takes a significant amount of
          time:
        Boundary {boundary_corner = (-8.6,-25.0), boundary_size = 0.1875}
        Boundary {boundary_corner = (-23.541666666666668,11.666666666666666), boundary_size = 20.7}

verification:
    The script "run_verify" compiles and executes the Verify.hs program. This is done in such a way
    that any data-spacepart package installed is hidden and the modules are sourced directly from
    the src folder. 
    The Verify.hs program just runs whatever QuickCheck tests I have thrown together. For each
    module under src there is a corresponding module under Verify that contains it's Arbitrary
    instances and verification properties.

    The script "run_visualize" compiles and executes the QuadTreeVisualize program. This will be
    compiled against the installed data-spacepart package. 
    The purpose of QuadTreeVisualize is to, well, visualize a random quadtree instance. in order to
    run this program it's necessary to have OpenGL bindings that support FBO. I have a branch with
    the required patches here:
        http://www.tothepowerofdisco.com/repo/OpenGL/

    The controls are:
        - arrow keys move left, up, right, down.
        - Shift-up and shift-down zoom in and zoom out respectively.

    This visualization program should not require the FBO dependency. However it was pulled from a
    different visualization system which did require FBOs. Removing this dependency is on the TODO
    list.

The version number of the library tries to follow the standard package version policy:
    http://www.haskell.org/haskellwiki/Package_versioning_policy

with the following addition: For the versiom number A.B.C.D D will be even for production releases
and odd for development versions.