Roc has the following refinements:
-- based on a C++ port of Gull 3, eliminating goto tatements.
-- fixes some minor bugs found in the Gull source
-- unit of valuation changed from 1 cp to 1/4 cp
-- extends Gull's two phases (opening, endgame) to 3 phases (opening, middle, endgame) plus a phase-like contribution for closed-ness
-- supports a contempt setting
-- adds king tropism to evaluation
In tests so far, Roc appears to be slightly stronger (5 +/- 5 Elo) than Gull 3.