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1 efrain 1 
<?php
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declare(strict_types=1);
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namespace Phpml\Math\Distance;
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use Phpml\Exception\InvalidArgumentException;
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use Phpml\Math\Distance as DistanceInterface;
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/**
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 * Class Distance
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 */
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abstract class Distance implements DistanceInterface
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{
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    /**
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     * @var float|int
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     */
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    public $norm;
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    /**
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     * Distance constructor.
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     */
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    public function __construct(float $norm = 3.0)
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    {
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        $this->norm = $norm;
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    }
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    /**
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     * @throws InvalidArgumentException
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     */
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    public function distance(array $a, array $b): float
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    {
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        $distance = 0;
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        foreach ($this->deltas($a, $b) as $delta) {
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            $distance += $delta ** $this->norm;
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        }
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        return $distance ** (1 / $this->norm);
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    }
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    /**
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     * @throws InvalidArgumentException
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     */
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    protected function deltas(array $a, array $b): array
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    {
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        $count = count($a);
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        if ($count !== count($b)) {
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            throw new InvalidArgumentException('Size of given arrays does not match');
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        }
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        $deltas = [];
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        for ($i = 0; $i < $count; $i++) {
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            $deltas[] = abs($a[$i] - $b[$i]);
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        }
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        return $deltas;
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    }
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}