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<?php |
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namespace Nubs\Geometron; |
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use Exception; |
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/** |
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* This class represents an immutable line segment in euclidean geometry and its |
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* associated operations. |
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* |
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* Instances of this class will not change state. Any operations on the line |
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* segment will return a new line segment with the new state. |
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*/ |
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class LineSegment implements Finite |
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{ |
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/** @type \Nubs\Geometron\Point One endpoint of the line segment. */ |
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protected $_a; |
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/** @type \Nubs\Geometron\Point One endpoint of the line segment. */ |
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protected $_b; |
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/** |
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* Initalize the line segment with its two endpoints. |
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* |
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* @api |
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* @param \Nubs\Geometron\Point $a One endpoint of the line segment. |
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* @param \Nubs\Geometron\Point $b One endpoint of the line segment. |
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*/ |
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public function __construct(Point $a, Point $b) |
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{ |
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if (!$a->isSameSpace($b)) { |
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throw new Exception('The two points must be in the same geometric space'); |
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} |
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$this->_a = $a; |
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$this->_b = $b; |
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} |
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/** |
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* Get an endpoint of the line segment. |
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* |
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* @api |
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* @return \Nubs\Geometron\Point One endpoint of the line segment. |
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*/ |
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public function a() |
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{ |
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return $this->_a; |
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} |
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/** |
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* Get an endpoint of the line segment. |
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* |
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* @api |
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* @return \Nubs\Geometron\Point One endpoint of the line segment. |
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*/ |
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public function b() |
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{ |
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return $this->_b; |
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} |
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/** |
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* Determine whether this line segment is degenerate. |
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* |
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* A line segment is degenerate if its two points are the same. |
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* |
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* @api |
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* @return bool True if the line segment is degenerate, false otherwise. |
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*/ |
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public function isDegenerate() |
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{ |
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return $this->a()->isEqual($this->b()); |
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} |
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/** |
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* Calculates the vector between the two endpoints of the line segment. |
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* |
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* @api |
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* @return \Nubs\Vectorix\Vector The vector from a() to b(). |
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*/ |
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public function vector() |
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{ |
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return $this->b()->vector()->subtract($this->a()->vector()); |
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} |
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/** |
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* Calculates the length of the line segment. |
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* |
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* @api |
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* @return float The length of the line segment. |
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*/ |
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public function length() |
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{ |
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return $this->vector()->length(); |
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} |
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/** |
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* The center of a line segment is the point halfway along the line. |
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* |
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* @api |
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* @return \Nubs\Geometron\Point The center-point of the line segment. |
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* @see \Nubs\Geometron\Finite::center() |
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*/ |
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public function center() |
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{ |
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return new Point($this->a()->vector()->add($this->vector()->divideByScalar(2))); |
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} |
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} |
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nubs /
geometron
