To count number of quadruplets with sum = 0

[mark.dufour at gmail.com]

> FWIW, the original program can also be compiled with Shed Skin (http://
> mark.dufour.googlepages.com), an experimental (static-)Python-to-C++
> compiler, resulting in a speedup of about 8 times for a single test
> with 500 tuples. here's a slightly modified version that works with
> Shed Skin CVS at least:

after optimizing dicts a bit for Shedskin 0.0.21 (http://
mark.dufour.googlepages.com), the speedup for this program is now
about 16.5 times for the same test.


Thanks,
Mark Dufour (Shed Skin author - send me bug reports!)