This is my current version of the code to compute broken lines and greedy
elements. Right now it is in a disgusting shape as far as style is concerned and
requires some major refactoring but at least it works.

To use it import in your sage session
sage: %attach scattering_diagrams.py

Disregard any other file: they are old experiments

--- OBSOLETE STUFF BEYOND THIS POINT
To use it import in your sage session
sage: %attach GreedyBasis.sage

There is a bug in the procedure to plot broken lines: the rays are not plotted
as they should be. To reproduce this bug do
sage: G=GreedyBasis(3,2)
sage: G.draw_broken_lines(8,8,(10,3))
you will see some scatterings happening not on the plotted ray