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<?php |
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declare(strict_types = 1); |
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namespace ExtendedStrings\Strings; |
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class Stop |
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{ |
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private $stringLength; |
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/** |
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* Stop constructor. |
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* |
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* @param float $stringLength The length of string that is left vibrating, |
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* as a fraction. |
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*/ |
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public function __construct(float $stringLength) |
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{ |
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if ($stringLength < 0 || $stringLength > 1) { |
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throw new \InvalidArgumentException(sprintf('Invalid string length: %f', $stringLength)); |
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} |
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$this->stringLength = $stringLength; |
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} |
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/** |
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* Create a Stop instance from a frequency over a string. |
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* |
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* @param float $frequency |
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* @param \ExtendedStrings\Strings\VibratingStringInterface $string |
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* |
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* @return \ExtendedStrings\Strings\Stop |
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*/ |
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public static function fromFrequency(float $frequency, VibratingStringInterface $string): self |
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{ |
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if (Math::isZero($frequency)) { |
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throw new \InvalidArgumentException(sprintf('Invalid frequency: %f', $frequency)); |
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} |
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$centsOverString = Cent::frequenciesToCents($string->getFrequency(), $frequency); |
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return new self(self::centsToStringLength($centsOverString)); |
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} |
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/** |
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* Returns the frequency of the stop (assuming normal pressure). |
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* |
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* @param VibratingStringInterface $string |
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* |
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* @return float |
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*/ |
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public function getFrequency(VibratingStringInterface $string): float |
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{ |
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$centsOverString = Cent::frequenciesToCents($this->stringLength, 1); |
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return Cent::centsToFrequency($centsOverString, $string->getFrequency()); |
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} |
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/** |
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* Returns the length of string that is left vibrating, as a fraction. |
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* |
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* @return float |
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*/ |
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public function getStringLength(): float |
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{ |
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return $this->stringLength; |
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} |
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/** |
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* Convert a number of cents over a string to a string length. |
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* |
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* @param float $cents The number of cents between the open string and the |
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* stopped pitch. |
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* |
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* @return float The length of the vibrating string, as a fraction of the |
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* whole string's length. |
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*/ |
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private static function centsToStringLength(float $cents): float |
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{ |
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return 1 / pow(2, $cents / 1200); |
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} |
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} |
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extended-strings /
strings
