/* Top level call */
AlphaBeta(state, 0, -inf, +inf, player)

function AlphaBeta(state, depth, alpha, beta, player)
    if CutoffTest(state, depth) then return (Eval(State), null)
    best = null /* handles early pruning or no possible move */
    if player == +1 then /* MAX player */
        for each action in Actions(state, player)
            (child, unused) = Result(state, action)
            value = AlphaBeta(child, depth+1, alpha, beta, -player)
            if value > alpha then
                alpha = value
                best = action
            if beta <= alpha then break /* beta cut-off */
        return (alpha, best)
    else /* MIN player */
        for each action in Actions(state, player)
            (child, unused) = Result(state, action)
            value = AlphaBeta(child, depth+1, alpha, beta, -player)
            if value < beta then
                beta = value
                best = action
            if beta <= alpha then break /* alpha cut-off */
        return (beta, best)
 end