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 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math3.geometry.euclidean.twod;

import org.apache.commons.math3.geometry.Point;
import org.apache.commons.math3.util.FastMath;

Simple container for a two-points segment.
Since:
3.0/** Simple container for a two-points segment.
 * @since 3.0
 */
public class Segment {

    
Start point of the segment. /** Start point of the segment. */
    private final Vector2D start;

    
End point of the segment. /** End point of the segment. */
    private final Vector2D end;

    
Line containing the segment. /** Line containing the segment. */
    private final Line     line;

    
Build a segment.
Params:
start – start point of the segment
end – end point of the segment
line – line containing the segment/** Build a segment.
     * @param start start point of the segment
     * @param end end point of the segment
     * @param line line containing the segment
     */
    public Segment(final Vector2D start, final Vector2D end, final Line line) {
        this.start  = start;
        this.end    = end;
        this.line   = line;
    }

    
Get the start point of the segment.
Returns:
start point of the segment/** Get the start point of the segment.
     * @return start point of the segment
     */
    public Vector2D getStart() {
        return start;
    }

    
Get the end point of the segment.
Returns:
end point of the segment/** Get the end point of the segment.
     * @return end point of the segment
     */
    public Vector2D getEnd() {
        return end;
    }

    
Get the line containing the segment.
Returns:
line containing the segment/** Get the line containing the segment.
     * @return line containing the segment
     */
    public Line getLine() {
        return line;
    }

    
Calculates the shortest distance from a point to this line segment.

If the perpendicular extension from the point to the line does not
cross in the bounds of the line segment, the shortest distance to
the two end points will be returned.

Algorithm adapted from:

Thread @ Codeguru
Params:
p – to check
Returns:
distance between the instance and the point
Since:
3.1/** Calculates the shortest distance from a point to this line segment.
     * <p>
     * If the perpendicular extension from the point to the line does not
     * cross in the bounds of the line segment, the shortest distance to
     * the two end points will be returned.
     * </p>
     *
     * Algorithm adapted from:
     * <a href="http://www.codeguru.com/forum/printthread.php?s=cc8cf0596231f9a7dba4da6e77c29db3&t=194400&pp=15&page=1">
     * Thread @ Codeguru</a>
     *
     * @param p to check
     * @return distance between the instance and the point
     * @since 3.1
     */
    public double distance(final Vector2D p) {
        final double deltaX = end.getX() - start.getX();
        final double deltaY = end.getY() - start.getY();

        final double r = ((p.getX() - start.getX()) * deltaX + (p.getY() - start.getY()) * deltaY) /
                         (deltaX * deltaX + deltaY * deltaY);

        // r == 0 => P = startPt
        // r == 1 => P = endPt
        // r < 0 => P is on the backward extension of the segment
        // r > 1 => P is on the forward extension of the segment
        // 0 < r < 1 => P is on the segment

        // if point isn't on the line segment, just return the shortest distance to the end points
        if (r < 0 || r > 1) {
            final double dist1 = getStart().distance((Point<Euclidean2D>) p);
            final double dist2 = getEnd().distance((Point<Euclidean2D>) p);

            return FastMath.min(dist1, dist2);
        }
        else {
            // find point on line and see if it is in the line segment
            final double px = start.getX() + r * deltaX;
            final double py = start.getY() + r * deltaY;

            final Vector2D interPt = new Vector2D(px, py);
            return interPt.distance((Point<Euclidean2D>) p);
        }
    }
}