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<?php
namespace lucidtaz\minimax\engine;
/**
* Alpha and beta pair for use in alpha/beta pruning
*/
class AlphaBeta
{
* @var float
public $alpha;
public $beta;
public function __construct(float $alpha, float $beta)
$this->alpha = $alpha;
$this->beta = $beta;
}
public static function initial(): AlphaBeta
return new static(-INF, INF);
* Update the constraint with new information
public function update(Evaluation $evaluation, NodeType $nodeType)
if ($nodeType == NodeType::MAX()) {
$this->alpha = max($this->alpha, $evaluation->score);
} elseif ($nodeType == NodeType::MIN()) {
$this->beta = min($this->beta, $evaluation->score);
* Check whether the value ranges (alpha..inf and -inf..beta) still overlap
* If not, the conclusion is that the game tree branch can be pruned.
public function isPositiveRange(): bool
return $this->alpha < $this->beta;
public function __toString(): string
return "($this->alpha, $this->beta)";
LucidTaZ /
minimax
