"Andrew Wagner"
current position (or, even more ideally, the so-called "principal variation", which is the best series of moves from the current position). Is there a good way to collect this, without mapping some sort of function over the tree that puts a list of moves on every node too?
Hughes seems to completely ignore this, and I wonder if it's because it gets ugly to implement.
While Hughes code looks nice, the more efficient you make your search the uglier it is going to be (at least with my Haskell skills) In reality you will at least want iterative deepening and principle variation search. I posted code for PVS (ugly code) http://www.haskell.org/haskellwiki/Principal_variation_search I thought I had some code doing iterative deepening based on this, but it looks like I lost it somewhere. If you want to use hash tables, history, killer moves, etc. Then I think you are going to have to monadize everything. It is a pity that Hughes doesn't demonstrate adding some of these things. Maybe it is possible using arrows? (without making everything look like C, which would be my solution). Rene.