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<?php |
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declare(strict_types=1); |
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namespace Ctefan\Kiwi; |
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/** |
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* A linear constraint equation. |
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* |
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* A constraint equation is composed of an expression, an operator, and a strength. |
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* The right hand side of the equation is implicitly zero. |
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*/ |
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class Constraint |
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{ |
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/** |
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* @var Expression |
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*/ |
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protected $expression; |
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/** |
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* @var float |
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*/ |
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protected $strength; |
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/** |
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* @var int |
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*/ |
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protected $operator; |
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/** |
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* Constraint constructor. |
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* |
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* @param Expression $expression |
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* @param int $operator |
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* @param float|null $strength |
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*/ |
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public function __construct(Expression $expression, int $operator, ?float $strength = null) |
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{ |
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$this->expression = self::reduce($expression); |
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$this->operator = $operator; |
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$this->strength = $strength ? Strength::clip($strength) : Strength::required(); |
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} |
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/** |
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* Create a Constraint from another Constraint. |
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* |
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* @param self $otherConstraint |
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* @param float $strength |
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* @return Constraint |
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*/ |
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static public function createFromConstraint(self $otherConstraint, float $strength): self |
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{ |
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return new self($otherConstraint->getExpression(), $otherConstraint->getOperator(), $strength); |
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} |
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/** |
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* @param Expression $expression |
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* @return Expression |
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*/ |
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static private function reduce(Expression $expression): Expression |
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{ |
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$variables = new \SplObjectStorage(); |
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foreach ($expression->getTerms() as $term) { |
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$variable = $term->getVariable(); |
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if (false === $variables->contains($variable)) { |
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$value = 0.0; |
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} else { |
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$value = $variables->offsetGet($variable); |
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} |
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$value += $term->getCoefficient(); |
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$variables->attach($variable, $value); |
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} |
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$reducedTerms = []; |
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foreach ($variables as $variable) { |
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$reducedTerms[] = new Term($variable, $variables->offsetGet($variable)); |
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} |
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return new Expression($reducedTerms, $expression->getConstant()); |
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} |
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/** |
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* @return Expression |
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*/ |
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public function getExpression(): Expression |
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{ |
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return $this->expression; |
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} |
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/** |
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* @param Expression $expression |
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*/ |
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public function setExpression(Expression $expression): void |
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{ |
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$this->expression = $expression; |
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} |
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/** |
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* @return float |
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*/ |
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public function getStrength(): float |
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{ |
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return $this->strength; |
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} |
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/** |
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* @param float $strength |
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* @return Constraint |
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*/ |
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public function setStrength(float $strength): self |
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{ |
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$this->strength = $strength; |
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return $this; |
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} |
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/** |
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* @return int |
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*/ |
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public function getOperator(): int |
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{ |
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return $this->operator; |
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} |
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/** |
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* @param int $operator |
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*/ |
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public function setOperator(int $operator): void |
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{ |
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$this->operator = $operator; |
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} |
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} |
Cmytxy /
kiwi-php
