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<?php |
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namespace Smoren\Sequence\Structs; |
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use function Smoren\Sequence\Functions\reduce; |
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use function Smoren\Sequence\Functions\xrange; |
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/** |
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* Implementation of sequence configured with callables. |
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* |
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* @template T |
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* @extends Sequence<T> |
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*/ |
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class DynamicSequence extends Sequence |
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{ |
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/** |
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* @var callable(T $previousValue): T getter for the next value |
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*/ |
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protected $nextValueGetter; |
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/** |
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* @var (callable(int $index, T $start): T)|null getter for the i-th value |
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*/ |
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protected $indexValueGetter; |
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/** |
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* StepSequence constructor. |
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* |
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* @param T $start start of the sequence |
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* @param int<0, max>|null $size size of the sequence (infinite if null) |
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* @param callable(T $previousValue): T $nextValueGetter getter for the next value |
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* @param (callable(int $index, T $start): T)|null $indexValueGetter getter for the i-th value |
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*/ |
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public function __construct( |
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$start, |
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?int $size, |
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callable $nextValueGetter, |
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?callable $indexValueGetter = null |
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) { |
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parent::__construct($start, $size); |
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$this->nextValueGetter = $nextValueGetter; |
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$this->indexValueGetter = $indexValueGetter; |
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} |
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/** |
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* {@inheritDoc} |
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*/ |
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public function getNextValue($previousValue) |
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{ |
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return ($this->nextValueGetter)($previousValue); |
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} |
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/** |
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* {@inheritDoc} |
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*/ |
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public function getValueByIndex(int $index) |
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{ |
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if(is_callable($this->indexValueGetter)) { |
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return ($this->indexValueGetter)($index, $this->start); |
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} |
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return reduce(xrange($index), function($carry) { |
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return $this->getNextValue($carry); |
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}, $this->start); |
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} |
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} |
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Smoren /
sequence-php
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