main/src/georegression/struct/shapes/Polygon2D_F64.java
public LineSegment2D_F64 getLine( int index , LineSegment2D_F64 storage ) {
		if( storage == null )
			storage = new LineSegment2D_F64();

		int j = (index+1)%vertexes.size;

		storage.a.set(get(index));
		storage.b.set(get(j));

		return storage;
	}
public LineSegment2D_F64 getLine( int index , LineSegment2D_F64 storage ) {
		if( storage == null )
			storage = new LineSegment2D_F64();

		int j = (index+1)%vertexes.size;

		storage.a.set(get(index));
		storage.b.set(get(j));

		return storage;
	}
Returns the line/edge defined by vertex index and index+1.
@param index Index of the line
@return A new instance of the line segment.