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/*******************************************************************************
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* Copyright (c) 2010 IBM Corporation and others.
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* All rights reserved. This program and the accompanying materials
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* are made available under the terms of the Eclipse Public License v1.0
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* which accompanies this distribution, and is available at
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* http://www.eclipse.org/legal/epl-v10.html
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*
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* Contributors:
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* Research Group Software Construction,
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* RWTH Aachen University, Germany - initial API and implementation
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*
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*******************************************************************************/
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package org.eclipse.draw2d.geometry;
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/**
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* Represents a straight line within 2-dimensional Euclidean space.
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*
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* @author Alexander Nyssen
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* @since 3.6
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*/
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public class Straight {
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/** position vector of this straight */
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public Vector position;
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/** direction vector of this straight */
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public Vector direction;
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/**
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* Constructs a new Straight with the given position and direction.
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*
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* @param position
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* @param direction
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*/
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public Straight(Vector position, Vector direction) {
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if (direction.isNull()) {
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throw new IllegalArgumentException(
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"direction has to be unequal to (0,0)"); //$NON-NLS-1$
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}
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this.position = position;
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this.direction = direction;
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}
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/**
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* Constructs a new Straight between the two given Points.
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*
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* @param point1
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* a first waypoint of the Straight to be constructed
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* @param point2
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* a second waypoint of the Straight to be constructed
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*/
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public Straight(PrecisionPoint point1, PrecisionPoint point2) {
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this(new Vector(point1), new Vector(point1, point2));
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}
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/**
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* Checks whether this Straight and the provided one have an intersection
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* point.
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*
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* @param other
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* The Straight to use for the calculation.
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* @return true if the two Straights intersect, false otherwise.
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*/
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public boolean intersects(Straight other) {
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return direction.getDotProduct(other.direction
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.getOrthogonalComplement()) != 0;
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}
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/**
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* Checks whether this Straight and the provided one have an intersection
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* point, which is inside the specified segment between segmentStart and
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* segmentEnd.
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*
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* segmentStart a Vector indicating the start point of the segment. Has to
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* be a point on the straight.
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*
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* @param segmentEnd
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* a Vector indicating the end point of the segment. Has to be a
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* point on the straight.
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* @param other
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* the Straight to test
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* @return true if the true straights intersect and the intersection point
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* is contained within the specified segment, false otherwise.
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* @since 3.2
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*/
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public boolean intersectsWithinSegment(Vector segmentStart,
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Vector segmentEnd, Straight other) {
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// precondition: segment start and end have to be points on this
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// straight.
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if (!contains(segmentStart) || !contains(segmentEnd)) {
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throw new IllegalArgumentException(
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"segment points have to be contained"); //$NON-NLS-1$
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}
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// check if segmentStart->segmentEnd is a legal segment or a single
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// point
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Vector segmentDirection = segmentEnd.getSubtracted(segmentStart);
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if (segmentDirection.isNull()) {
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return other.contains(segmentStart);
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}
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// legal segment, check if there is an intersection within the segment
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if (intersects(other)) {
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Vector intersection = getIntersection(other);
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return containsWithinSegment(segmentStart, segmentEnd, intersection);
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}
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return false;
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}
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/**
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* Computes the intersection point of this Straight and the provided one, if
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* it exists.
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*
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* @param other
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* The Straight to use for calculations.
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* @return A Vector pointing to the intersection point, if it exists, null
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* if no intersection point exists (or the Straights are equal).
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*/
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public Vector getIntersection(Straight other) {
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// first check if there is a single intersection point
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if (!intersects(other)) {
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return null;
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}
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// calculate intersection point
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Vector s1 = direction.getMultiplied(other.position
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.getDotProduct(other.direction.getOrthogonalComplement()));
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Vector s2 = other.direction.getMultiplied(position
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.getDotProduct(direction.getOrthogonalComplement()));
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return s1.getSubtracted(s2).getDivided(
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direction.getDotProduct(other.direction
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.getOrthogonalComplement()));
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}
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/**
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* Returns the (smallest) angle between this Straight and the provided one.
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*
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* @param other
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* The Straight to be used for the calculation.
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* @return The angle spanned between the two Straights.
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*/
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public double getAngle(Straight other) {
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return direction.getAngle(other.direction);
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}
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/**
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* Returns the projection of the given Vector onto this Straight, which is
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* the point on this Straight with the minimal distance to the point,
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* denoted by the provided Vector.
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*
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* @param vector
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* The Vector whose projection should be determined.
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* @return A new Vector representing the projection of the provided Vector
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* onto this Straight.
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*/
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public Vector getProjection(Vector vector) {
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return getIntersection(new Straight(vector,
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direction.getOrthogonalComplement()));
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}
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/**
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* Returns the distance of the provided Vector to this Straight, which is
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* the distance between the provided Vector and its projection onto this
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* Straight.
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*
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* @param vector
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* The Vector whose distance is to be calculated.
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* @return the distance between this Straight and the provided Vector.
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*/
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public double getDistance(Vector vector) {
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return getProjection(vector).getSubtracted(vector).getLength();
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}
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/**
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* Calculates whether the point indicated by the provided Vector is a point
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* on this Straight.
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*
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* @param vector
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* the Vector who has to be checked.
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* @return true if the point indicated by the given Vector is a point of
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* this Straight, false otherwise.
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*/
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public boolean contains(Vector vector) {
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return getDistance(vector) == 0;
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}
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/**
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* Calculates whether the point indicated by the provided Vector is a point
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* on the straight segment between the given start and end points.
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*
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* @param segmentStart
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* a Vector indicating the start point of the segment. Has to be
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* a point on the straight.
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* @param segmentEnd
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* a Vector indicating the end point of the segment. Has to be a
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* point on the straight.
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* @param vector
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* the Vector who has to be checked.
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* @return true if point indicated by the given Vector is a point on this
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* straight, within the specified segment, false otherwise.
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*/
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public boolean containsWithinSegment(Vector segmentStart,
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Vector segmentEnd, Vector vector) {
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// precondition: segment start and end have to be points on this
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// straight.
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if (!contains(segmentStart) || !contains(segmentEnd)) {
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throw new IllegalArgumentException(
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"segment points have to be contained"); //$NON-NLS-1$
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}
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// check if segmentStart->segmentEnd is a legal segment or a single
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// point
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Vector segmentDirection = segmentEnd.getSubtracted(segmentStart);
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if (segmentDirection.isNull()) {
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return segmentStart.equals(vector);
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}
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// legal segment
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if (new Straight(segmentStart, segmentDirection).contains(vector)) {
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// compute parameter s, so that vector = segmentStart + s *
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// (segmentEnd - segmentStart).
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double s = segmentDirection.isVertical() ? (vector.y - segmentDirection.y)
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/ segmentDirection.y
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: (vector.x - segmentStart.x) / segmentDirection.x;
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// if s is between 0 and 1, intersection point lies within
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// segment
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if (0 <= s && s <= 1) {
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return true;
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}
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}
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return false;
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}
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/**
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* Checks whether this Straight and the provided one are parallel to each
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* other.
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*
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* @param other
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* The Straight to test for parallelism.
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* @return true if the direction vectors of this Straight and the provided
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* one are parallel, false otherwise.
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*/
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public boolean isParallelTo(Straight other) {
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return direction.isParallelTo(other.direction);
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}
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/**
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* Checks whether this Straight is equal to the provided Straight. Two
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* Straights s1 and s2 are equal, if the position vector of s2 is a point on
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* s1 and the direction vectors of s1 and s2 are parallel.
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*
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* @see java.lang.Object#equals(java.lang.Object)
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*/
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public boolean equals(Object other) {
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if (!(other instanceof Straight)) {
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return false;
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} else {
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Straight otherStraight = (Straight) other;
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return contains(otherStraight.position)
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&& isParallelTo(otherStraight);
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}
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}
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/**
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* @see java.lang.Object#hashCode()
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*/
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public int hashCode() {
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return position.hashCode() + direction.hashCode();
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}
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/**
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* @see java.lang.Object#toString()
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*/
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public String toString() {
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return position.toString() + " + s * " + direction.toString(); //$NON-NLS-1$
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}
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}
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