alpha beta pruning is incomplete

[GoogleCodeExporter]

the use of argmax() for the first max node in the alpha beta pruning searches 
will not allow alpha pruning to be updated among the min successors of the 
initial max mode.  code in question:

    # Body of alphabeta_search:
    return argmax(game.actions(state),
                  lambda a: min_value(game.result(state, a),
                                      -infinity, infinity))

alpha will always be -infinity instead of a value discovered in a previous min 
child/successor.

Original issue reported on code.google.com by chasmosa...@gmail.com on 22 Nov 2012 at 10:16