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<?php |
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namespace drupol\phpermutations\Iterators; |
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use drupol\phpermutations\Combinatorics; |
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/** |
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* Class PrimeSieveOfAtkin. |
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* |
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* @package drupol\phpermutations\Iterators |
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*/ |
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class PrimeSieveOfAtkin extends Combinatorics implements \Iterator, \Countable { |
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/** |
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* The minimum limit. |
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* |
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* @var int |
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*/ |
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protected $min; |
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/** |
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* The maximum limit. |
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* |
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* @var int |
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*/ |
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protected $max; |
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/** |
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* The key. |
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* |
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* @var int |
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*/ |
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protected $key; |
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/** |
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* The primes array. |
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* |
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* @var array |
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*/ |
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protected $primesData; |
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/** |
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* The primes array. |
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* |
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* @var array |
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*/ |
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protected $primes; |
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/** |
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* The primes array converted. |
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* |
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* @var array |
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*/ |
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protected $data; |
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/** |
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* @var int |
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*/ |
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private $last; |
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private $count; |
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/** |
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* PrimeSieveOfAtkin constructor. |
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*/ |
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public function __construct() { |
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$this->primesData = new \ArrayObject(array(2 => 1, 3 => 1)); |
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$this->primes = array(2, 3); |
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$this->setMinLimit(0); |
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$this->max = PHP_INT_MAX; |
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} |
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private function generateNextPrime() { |
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$candidate = $limit = end($this->primes); |
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do { |
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$candidate += 2; |
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$primes = $this->findPrimes($candidate); |
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} while (!isset($primes[$this->key()])); |
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return array_keys($primes); |
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} |
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/** |
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* @param $index |
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*/ |
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private function toggle(&$primes, $index) { |
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if (!isset($primes[$index])) { |
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$primes[$index] = FALSE; |
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} |
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$primes[$index] ^= TRUE; |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function current() { |
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if (!isset($this->primes[$this->key()])) { |
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$this->primes = $this->generateNextPrime(); |
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} |
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return $this->primes[$this->key()]; |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function valid() { |
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return ($this->current() < $this->getMaxLimit()); |
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} |
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public function findPrimes($limit) { |
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$sqrt = sqrt($limit); |
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$isPrime = array(); |
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for ($i = 1; $i <= $sqrt; $i++) { |
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for ($j = 1; $j <= $sqrt; $j++) { |
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$n = 4 * pow($i, 2) + pow($j, 2); |
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if ($n <= $limit && ($n % 12 == 1 || $n % 12 == 5)) { |
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$this->toggle($isPrime, $n); |
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} |
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$n = 3 * pow($i, 2) + pow($j, 2); |
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if ($n <= $limit && $n % 12 == 7) { |
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$this->toggle($isPrime, $n); |
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} |
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$n = 3 * pow($i, 2) - pow($j, 2); |
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if ($i > $j && $n <= $limit && $n % 12 == 11) { |
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$this->toggle($isPrime, $n); |
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} |
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} |
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} |
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for ($n = 5; $n <= $sqrt; $n++) { |
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if (isset($isPrime[$n])) { |
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$s = pow($n, 2); |
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for ($k = $s; $k <= $limit; $k += $s) { |
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$isPrime[$k] = FALSE; |
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} |
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} |
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} |
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$primes[2] = 2; |
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$primes[3] = 3; |
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for ($i = 0; $i < $limit; $i++) { |
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if (isset($isPrime[$i]) && $isPrime[$i]) { |
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$primes[$i] = $i; |
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} |
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} |
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return $primes; |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function rewind() { |
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$this->key = 0; |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function key() { |
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return $this->key; |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function next() { |
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++$this->key; |
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} |
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/** |
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* Count elements of an object. |
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* |
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* @return int |
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* The number of element. |
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*/ |
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public function count() { |
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return count($this->toArray()); |
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} |
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/** |
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* Convert the iterator into an array. |
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* |
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* @return array |
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* The elements. |
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*/ |
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public function toArray() { |
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$data = array(); |
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for ($this->rewind(); $this->valid(); $this->next()) { |
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$data[] = $this->current(); |
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} |
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return $data; |
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} |
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/** |
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* Set the maximum limit. |
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* |
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* @param int $max |
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* The limit. |
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*/ |
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public function setMaxLimit($max) { |
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$this->max = $max; |
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$this->primes = array_keys($this->findPrimes($this->max)); |
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} |
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/** |
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* Get the maximum limit. |
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* |
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* @return int |
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* The limit. |
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*/ |
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public function getMaxLimit() { |
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return $this->max; |
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} |
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/** |
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* Set the minimum limit. |
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* |
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* @param int $min |
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* The limit. |
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*/ |
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public function setMinLimit($min) { |
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$this->min = $min; |
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} |
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/** |
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* Get the minimum limit. |
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* |
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* @return int |
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* The limit. |
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*/ |
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public function getMinLimit() { |
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return $this->min <= 2 ? 2 : intval($this->min); |
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} |
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/** |
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* Get a rough estimation of how many prime numbers there are. |
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* |
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* @return float |
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* The number of primes. |
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*/ |
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public function pi() { |
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return $this->getMaxLimit() / log($this->getMaxLimit()); |
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} |
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} |
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This check marks private properties in classes that are never used. Those properties can be removed.