1 /*
  2     Copyright 2008-2024
  3         Matthias Ehmann,
  4         Michael Gerhaeuser,
  5         Carsten Miller,
  6         Bianca Valentin,
  7         Alfred Wassermann,
  8         Peter Wilfahrt
  9 
 10     This file is part of JSXGraph.
 11 
 12     JSXGraph is free software dual licensed under the GNU LGPL or MIT License.
 13 
 14     You can redistribute it and/or modify it under the terms of the
 15 
 16       * GNU Lesser General Public License as published by
 17         the Free Software Foundation, either version 3 of the License, or
 18         (at your option) any later version
 19       OR
 20       * MIT License: https://github.com/jsxgraph/jsxgraph/blob/master/LICENSE.MIT
 21 
 22     JSXGraph is distributed in the hope that it will be useful,
 23     but WITHOUT ANY WARRANTY; without even the implied warranty of
 24     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 25     GNU Lesser General Public License for more details.
 26 
 27     You should have received a copy of the GNU Lesser General Public License and
 28     the MIT License along with JSXGraph. If not, see <https://www.gnu.org/licenses/>
 29     and <https://opensource.org/licenses/MIT/>.
 30  */
 31 
 32 /*global JXG: true, define: true*/
 33 /*jslint nomen: true, plusplus: true*/
 34 
 35 /**
 36  * @fileoverview In this file the geometry element Curve is defined.
 37  */
 38 
 39 import JXG from "../jxg.js";
 40 import Clip from "../math/clip.js";
 41 import Const from "./constants.js";
 42 import Coords from "./coords.js";
 43 import Geometry from "../math/geometry.js";
 44 import GeometryElement from "./element.js";
 45 import GeonextParser from "../parser/geonext.js";
 46 import ImplicitPlot from "../math/implicitplot.js";
 47 import Mat from "../math/math.js";
 48 import Metapost from "../math/metapost.js";
 49 import Numerics from "../math/numerics.js";
 50 import Plot from "../math/plot.js";
 51 import QDT from "../math/qdt.js";
 52 import Type from "../utils/type.js";
 53 
 54 /**
 55  * Curves are the common object for function graphs, parametric curves, polar curves, and data plots.
 56  * @class Creates a new curve object. Do not use this constructor to create a curve. Use {@link JXG.Board#create} with
 57  * type {@link Curve}, or {@link Functiongraph} instead.
 58  * @augments JXG.GeometryElement
 59  * @param {String|JXG.Board} board The board the new curve is drawn on.
 60  * @param {Array} parents defining terms An array with the function terms or the data points of the curve.
 61  * @param {Object} attributes Defines the visual appearance of the curve.
 62  * @see JXG.Board#generateName
 63  * @see JXG.Board#addCurve
 64  */
 65 JXG.Curve = function (board, parents, attributes) {
 66     this.constructor(board, attributes, Const.OBJECT_TYPE_CURVE, Const.OBJECT_CLASS_CURVE);
 67 
 68     this.points = [];
 69     /**
 70      * Number of points on curves. This value changes
 71      * between numberPointsLow and numberPointsHigh.
 72      * It is set in {@link JXG.Curve#updateCurve}.
 73      */
 74     this.numberPoints = this.evalVisProp('numberpointshigh');
 75 
 76     this.bezierDegree = 1;
 77 
 78     /**
 79      * Array holding the x-coordinates of a data plot.
 80      * This array can be updated during run time by overwriting
 81      * the method {@link JXG.Curve#updateDataArray}.
 82      * @type array
 83      */
 84     this.dataX = null;
 85 
 86     /**
 87      * Array holding the y-coordinates of a data plot.
 88      * This array can be updated during run time by overwriting
 89      * the method {@link JXG.Curve#updateDataArray}.
 90      * @type array
 91      */
 92     this.dataY = null;
 93 
 94     /**
 95      * Array of ticks storing all the ticks on this curve. Do not set this field directly and use
 96      * {@link JXG.Curve#addTicks} and {@link JXG.Curve#removeTicks} to add and remove ticks to and
 97      * from the curve.
 98      * @type Array
 99      * @see JXG.Ticks
100      */
101     this.ticks = [];
102 
103     /**
104      * Stores a quadtree if it is required. The quadtree is generated in the curve
105      * updates and can be used to speed up the hasPoint method.
106      * @type JXG.Math.Quadtree
107      */
108     this.qdt = null;
109 
110     if (Type.exists(parents[0])) {
111         this.varname = parents[0];
112     } else {
113         this.varname = "x";
114     }
115 
116     // function graphs: "x"
117     this.xterm = parents[1];
118     // function graphs: e.g. "x^2"
119     this.yterm = parents[2];
120 
121     // Converts GEONExT syntax into JavaScript syntax
122     this.generateTerm(this.varname, this.xterm, this.yterm, parents[3], parents[4]);
123     // First evaluation of the curve
124     this.updateCurve();
125 
126     this.id = this.board.setId(this, "G");
127     this.board.renderer.drawCurve(this);
128 
129     this.board.finalizeAdding(this);
130 
131     this.createGradient();
132     this.elType = "curve";
133     this.createLabel();
134 
135     if (Type.isString(this.xterm)) {
136         this.notifyParents(this.xterm);
137     }
138     if (Type.isString(this.yterm)) {
139         this.notifyParents(this.yterm);
140     }
141 
142     this.methodMap = Type.deepCopy(this.methodMap, {
143         generateTerm: "generateTerm",
144         setTerm: "generateTerm",
145         move: "moveTo",
146         moveTo: "moveTo",
147         MinX: "minX",
148         MaxX: "maxX"
149     });
150 };
151 
152 JXG.Curve.prototype = new GeometryElement();
153 
154 JXG.extend(
155     JXG.Curve.prototype,
156     /** @lends JXG.Curve.prototype */ {
157         /**
158          * Gives the default value of the left bound for the curve.
159          * May be overwritten in {@link JXG.Curve#generateTerm}.
160          * @returns {Number} Left bound for the curve.
161          */
162         minX: function () {
163             var leftCoords;
164 
165             if (this.evalVisProp('curvetype') === "polar") {
166                 return 0;
167             }
168 
169             leftCoords = new Coords(
170                 Const.COORDS_BY_SCREEN,
171                 [-this.board.canvasWidth * 0.1, 0],
172                 this.board,
173                 false
174             );
175             return leftCoords.usrCoords[1];
176         },
177 
178         /**
179          * Gives the default value of the right bound for the curve.
180          * May be overwritten in {@link JXG.Curve#generateTerm}.
181          * @returns {Number} Right bound for the curve.
182          */
183         maxX: function () {
184             var rightCoords;
185 
186             if (this.evalVisProp('curvetype') === "polar") {
187                 return 2 * Math.PI;
188             }
189             rightCoords = new Coords(
190                 Const.COORDS_BY_SCREEN,
191                 [this.board.canvasWidth * 1.1, 0],
192                 this.board,
193                 false
194             );
195 
196             return rightCoords.usrCoords[1];
197         },
198 
199         /**
200          * The parametric function which defines the x-coordinate of the curve.
201          * @param {Number} t A number between {@link JXG.Curve#minX} and {@link JXG.Curve#maxX}.
202          * @param {Boolean} suspendUpdate A boolean flag which is false for the
203          * first call of the function during a fresh plot of the curve and true
204          * for all subsequent calls of the function. This may be used to speed up the
205          * plotting of the curve, if the e.g. the curve depends on some input elements.
206          * @returns {Number} x-coordinate of the curve at t.
207          */
208         X: function (t) {
209             return NaN;
210         },
211 
212         /**
213          * The parametric function which defines the y-coordinate of the curve.
214          * @param {Number} t A number between {@link JXG.Curve#minX} and {@link JXG.Curve#maxX}.
215          * @param {Boolean} suspendUpdate A boolean flag which is false for the
216          * first call of the function during a fresh plot of the curve and true
217          * for all subsequent calls of the function. This may be used to speed up the
218          * plotting of the curve, if the e.g. the curve depends on some input elements.
219          * @returns {Number} y-coordinate of the curve at t.
220          */
221         Y: function (t) {
222             return NaN;
223         },
224 
225         /**
226          * Treat the curve as curve with homogeneous coordinates.
227          * @param {Number} t A number between {@link JXG.Curve#minX} and {@link JXG.Curve#maxX}.
228          * @returns {Number} Always 1.0
229          */
230         Z: function (t) {
231             return 1;
232         },
233 
234         /**
235          * Checks whether (x,y) is near the curve.
236          * @param {Number} x Coordinate in x direction, screen coordinates.
237          * @param {Number} y Coordinate in y direction, screen coordinates.
238          * @param {Number} start Optional start index for search on data plots.
239          * @returns {Boolean} True if (x,y) is near the curve, False otherwise.
240          */
241         hasPoint: function (x, y, start) {
242             var t, c, i, tX, tY,
243                 checkPoint, len, invMat, isIn,
244                 res = [],
245                 points,
246                 qdt,
247                 steps = this.evalVisProp('numberpointslow'),
248                 d = (this.maxX() - this.minX()) / steps,
249                 prec, type,
250                 dist = Infinity,
251                 ux2, uy2,
252                 ev_ct,
253                 mi, ma,
254                 suspendUpdate = true;
255 
256             if (Type.isObject(this.evalVisProp('precision'))) {
257                 type = this.board._inputDevice;
258                 prec = this.evalVisProp('precision.' + type);
259             } else {
260                 // 'inherit'
261                 prec = this.board.options.precision.hasPoint;
262             }
263 
264             // From now on, x,y are usrCoords
265             checkPoint = new Coords(Const.COORDS_BY_SCREEN, [x, y], this.board, false);
266             x = checkPoint.usrCoords[1];
267             y = checkPoint.usrCoords[2];
268 
269             // Handle inner points of the curve
270             if (this.bezierDegree === 1 && this.evalVisProp('hasinnerpoints')) {
271                 isIn = Geometry.windingNumber([1, x, y], this.points, true);
272                 if (isIn !== 0) {
273                     return true;
274                 }
275             }
276 
277             // We use usrCoords. Only in the final distance calculation
278             // screen coords are used
279             prec += this.evalVisProp('strokewidth') * 0.5;
280             prec *= prec; // We do not want to take sqrt
281             ux2 = this.board.unitX * this.board.unitX;
282             uy2 = this.board.unitY * this.board.unitY;
283 
284             mi = this.minX();
285             ma = this.maxX();
286             if (Type.exists(this._visibleArea)) {
287                 mi = this._visibleArea[0];
288                 ma = this._visibleArea[1];
289                 d = (ma - mi) / steps;
290             }
291 
292             ev_ct = this.evalVisProp('curvetype');
293             if (ev_ct === "parameter" || ev_ct === "polar") {
294                 // Transform the mouse/touch coordinates
295                 // back to the original position of the curve.
296                 // This is needed, because we work with the function terms, not the points.
297                 if (this.transformations.length > 0) {
298                     this.updateTransformMatrix();
299                     invMat = Mat.inverse(this.transformMat);
300                     c = Mat.matVecMult(invMat, [1, x, y]);
301                     x = c[1];
302                     y = c[2];
303                 }
304 
305                 // Brute force search for a point on the curve close to the mouse pointer
306                 for (i = 0, t = mi; i < steps; i++) {
307                     tX = this.X(t, suspendUpdate);
308                     tY = this.Y(t, suspendUpdate);
309 
310                     dist = (x - tX) * (x - tX) * ux2 + (y - tY) * (y - tY) * uy2;
311 
312                     if (dist <= prec) {
313                         return true;
314                     }
315 
316                     t += d;
317                 }
318             } else if (ev_ct === "plot" || ev_ct === "functiongraph") {
319                 // Here, we can ignore transformations of the curve,
320                 // since we are working directly with the points.
321 
322                 if (!Type.exists(start) || start < 0) {
323                     start = 0;
324                 }
325 
326                 if (
327                     Type.exists(this.qdt) &&
328                     this.evalVisProp('useqdt') &&
329                     this.bezierDegree !== 3
330                 ) {
331                     qdt = this.qdt.query(new Coords(Const.COORDS_BY_USER, [x, y], this.board));
332                     points = qdt.points;
333                     len = points.length;
334                 } else {
335                     points = this.points;
336                     len = this.numberPoints - 1;
337                 }
338 
339                 for (i = start; i < len; i++) {
340                     if (this.bezierDegree === 3) {
341                         //res.push(Geometry.projectCoordsToBeziersegment([1, x, y], this, i));
342                         res = Geometry.projectCoordsToBeziersegment([1, x, y], this, i);
343                     } else {
344                         if (qdt) {
345                             if (points[i].prev) {
346                                 res = Geometry.projectCoordsToSegment(
347                                     [1, x, y],
348                                     points[i].prev.usrCoords,
349                                     points[i].usrCoords
350                                 );
351                             }
352 
353                             // If the next point in the array is the same as the current points
354                             // next neighbor we don't have to project it onto that segment because
355                             // that will already be done in the next iteration of this loop.
356                             if (points[i].next && points[i + 1] !== points[i].next) {
357                                 res = Geometry.projectCoordsToSegment(
358                                     [1, x, y],
359                                     points[i].usrCoords,
360                                     points[i].next.usrCoords
361                                 );
362                             }
363                         } else {
364                             res = Geometry.projectCoordsToSegment(
365                                 [1, x, y],
366                                 points[i].usrCoords,
367                                 points[i + 1].usrCoords
368                             );
369                         }
370                     }
371 
372                     if (
373                         res[1] >= 0 &&
374                         res[1] <= 1 &&
375                         (x - res[0][1]) * (x - res[0][1]) * ux2 +
376                         (y - res[0][2]) * (y - res[0][2]) * uy2 <=
377                         prec
378                     ) {
379                         return true;
380                     }
381                 }
382                 return false;
383             }
384             return dist < prec;
385         },
386 
387         /**
388          * Allocate points in the Coords array this.points
389          */
390         allocatePoints: function () {
391             var i, len;
392 
393             len = this.numberPoints;
394 
395             if (this.points.length < this.numberPoints) {
396                 for (i = this.points.length; i < len; i++) {
397                     this.points[i] = new Coords(
398                         Const.COORDS_BY_USER,
399                         [0, 0],
400                         this.board,
401                         false
402                     );
403                 }
404             }
405         },
406 
407         /**
408          * Computes for equidistant points on the x-axis the values of the function
409          * @returns {JXG.Curve} Reference to the curve object.
410          * @see JXG.Curve#updateCurve
411          */
412         update: function () {
413             if (this.needsUpdate) {
414                 if (this.evalVisProp('trace')) {
415                     this.cloneToBackground(true);
416                 }
417                 this.updateCurve();
418             }
419 
420             return this;
421         },
422 
423         /**
424          * Updates the visual contents of the curve.
425          * @returns {JXG.Curve} Reference to the curve object.
426          */
427         updateRenderer: function () {
428             //var wasReal;
429 
430             if (!this.needsUpdate) {
431                 return this;
432             }
433 
434             if (this.visPropCalc.visible) {
435                 // wasReal = this.isReal;
436 
437                 this.isReal = Plot.checkReal(this.points);
438 
439                 if (
440                     //wasReal &&
441                     !this.isReal
442                 ) {
443                     this.updateVisibility(false);
444                 }
445             }
446 
447             if (this.visPropCalc.visible) {
448                 this.board.renderer.updateCurve(this);
449             }
450 
451             /* Update the label if visible. */
452             if (
453                 this.hasLabel &&
454                 this.visPropCalc.visible &&
455                 this.label &&
456                 this.label.visPropCalc.visible &&
457                 this.isReal
458             ) {
459                 this.label.update();
460                 this.board.renderer.updateText(this.label);
461             }
462 
463             // Update rendNode display
464             this.setDisplayRendNode();
465             // if (this.visPropCalc.visible !== this.visPropOld.visible) {
466             //     this.board.renderer.display(this, this.visPropCalc.visible);
467             //     this.visPropOld.visible = this.visPropCalc.visible;
468             //
469             //     if (this.hasLabel) {
470             //         this.board.renderer.display(this.label, this.label.visPropCalc.visible);
471             //     }
472             // }
473 
474             this.needsUpdate = false;
475             return this;
476         },
477 
478         /**
479          * For dynamic dataplots updateCurve can be used to compute new entries
480          * for the arrays {@link JXG.Curve#dataX} and {@link JXG.Curve#dataY}. It
481          * is used in {@link JXG.Curve#updateCurve}. Default is an empty method, can
482          * be overwritten by the user.
483          *
484          *
485          * @example
486          * // This example overwrites the updateDataArray method.
487          * // There, new values for the arrays JXG.Curve.dataX and JXG.Curve.dataY
488          * // are computed from the value of the slider N
489          *
490          * var N = board.create('slider', [[0,1.5],[3,1.5],[1,3,40]], {name:'n',snapWidth:1});
491          * var circ = board.create('circle',[[4,-1.5],1],{strokeWidth:1, strokecolor:'black', strokeWidth:2,
492          * 		fillColor:'#0055ff13'});
493          *
494          * var c = board.create('curve', [[0],[0]],{strokecolor:'red', strokeWidth:2});
495          * c.updateDataArray = function() {
496          *         var r = 1, n = Math.floor(N.Value()),
497          *             x = [0], y = [0],
498          *             phi = Math.PI/n,
499          *             h = r*Math.cos(phi),
500          *             s = r*Math.sin(phi),
501          *             i, j,
502          *             px = 0, py = 0, sgn = 1,
503          *             d = 16,
504          *             dt = phi/d,
505          *             pt;
506          *
507          *         for (i = 0; i < n; i++) {
508          *             for (j = -d; j <= d; j++) {
509          *                 pt = dt*j;
510          *                 x.push(px + r*Math.sin(pt));
511          *                 y.push(sgn*r*Math.cos(pt) - (sgn-1)*h*0.5);
512          *             }
513          *             px += s;
514          *             sgn *= (-1);
515          *         }
516          *         x.push((n - 1)*s);
517          *         y.push(h + (sgn - 1)*h*0.5);
518          *         this.dataX = x;
519          *         this.dataY = y;
520          *     }
521          *
522          * var c2 = board.create('curve', [[0],[0]],{strokecolor:'red', strokeWidth:1});
523          * c2.updateDataArray = function() {
524          *         var r = 1, n = Math.floor(N.Value()),
525          *             px = circ.midpoint.X(), py = circ.midpoint.Y(),
526          *             x = [px], y = [py],
527          *             phi = Math.PI/n,
528          *             s = r*Math.sin(phi),
529          *             i, j,
530          *             d = 16,
531          *             dt = phi/d,
532          *             pt = Math.PI*0.5+phi;
533          *
534          *         for (i = 0; i < n; i++) {
535          *             for (j= -d; j <= d; j++) {
536          *                 x.push(px + r*Math.cos(pt));
537          *                 y.push(py + r*Math.sin(pt));
538          *                 pt -= dt;
539          *             }
540          *             x.push(px);
541          *             y.push(py);
542          *             pt += dt;
543          *         }
544          *         this.dataX = x;
545          *         this.dataY = y;
546          *     }
547          *     board.update();
548          *
549          * </pre><div id="JXG20bc7802-e69e-11e5-b1bf-901b0e1b8723" class="jxgbox" style="width: 600px; height: 400px;"></div>
550          * <script type="text/javascript">
551          *     (function() {
552          *         var board = JXG.JSXGraph.initBoard('JXG20bc7802-e69e-11e5-b1bf-901b0e1b8723',
553          *             {boundingbox: [-1.5,2,8,-3], keepaspectratio: true, axis: true, showcopyright: false, shownavigation: false});
554          *             var N = board.create('slider', [[0,1.5],[3,1.5],[1,3,40]], {name:'n',snapWidth:1});
555          *             var circ = board.create('circle',[[4,-1.5],1],{strokeWidth:1, strokecolor:'black',
556          *             strokeWidth:2, fillColor:'#0055ff13'});
557          *
558          *             var c = board.create('curve', [[0],[0]],{strokecolor:'red', strokeWidth:2});
559          *             c.updateDataArray = function() {
560          *                     var r = 1, n = Math.floor(N.Value()),
561          *                         x = [0], y = [0],
562          *                         phi = Math.PI/n,
563          *                         h = r*Math.cos(phi),
564          *                         s = r*Math.sin(phi),
565          *                         i, j,
566          *                         px = 0, py = 0, sgn = 1,
567          *                         d = 16,
568          *                         dt = phi/d,
569          *                         pt;
570          *
571          *                     for (i=0;i<n;i++) {
572          *                         for (j=-d;j<=d;j++) {
573          *                             pt = dt*j;
574          *                             x.push(px+r*Math.sin(pt));
575          *                             y.push(sgn*r*Math.cos(pt)-(sgn-1)*h*0.5);
576          *                         }
577          *                         px += s;
578          *                         sgn *= (-1);
579          *                     }
580          *                     x.push((n-1)*s);
581          *                     y.push(h+(sgn-1)*h*0.5);
582          *                     this.dataX = x;
583          *                     this.dataY = y;
584          *                 }
585          *
586          *             var c2 = board.create('curve', [[0],[0]],{strokecolor:'red', strokeWidth:1});
587          *             c2.updateDataArray = function() {
588          *                     var r = 1, n = Math.floor(N.Value()),
589          *                         px = circ.midpoint.X(), py = circ.midpoint.Y(),
590          *                         x = [px], y = [py],
591          *                         phi = Math.PI/n,
592          *                         s = r*Math.sin(phi),
593          *                         i, j,
594          *                         d = 16,
595          *                         dt = phi/d,
596          *                         pt = Math.PI*0.5+phi;
597          *
598          *                     for (i=0;i<n;i++) {
599          *                         for (j=-d;j<=d;j++) {
600          *                             x.push(px+r*Math.cos(pt));
601          *                             y.push(py+r*Math.sin(pt));
602          *                             pt -= dt;
603          *                         }
604          *                         x.push(px);
605          *                         y.push(py);
606          *                         pt += dt;
607          *                     }
608          *                     this.dataX = x;
609          *                     this.dataY = y;
610          *                 }
611          *                 board.update();
612          *
613          *     })();
614          *
615          * </script><pre>
616          *
617          * @example
618          * // This is an example which overwrites updateDataArray and produces
619          * // a Bezier curve of degree three.
620          * var A = board.create('point', [-3,3]);
621          * var B = board.create('point', [3,-2]);
622          * var line = board.create('segment', [A,B]);
623          *
624          * var height = 0.5; // height of the curly brace
625          *
626          * // Curly brace
627          * var crl = board.create('curve', [[0],[0]], {strokeWidth:1, strokeColor:'black'});
628          * crl.bezierDegree = 3;
629          * crl.updateDataArray = function() {
630          *     var d = [B.X()-A.X(), B.Y()-A.Y()],
631          *         dl = Math.sqrt(d[0]*d[0]+d[1]*d[1]),
632          *         mid = [(A.X()+B.X())*0.5, (A.Y()+B.Y())*0.5];
633          *
634          *     d[0] *= height/dl;
635          *     d[1] *= height/dl;
636          *
637          *     this.dataX = [ A.X(), A.X()-d[1], mid[0], mid[0]-d[1], mid[0], B.X()-d[1], B.X() ];
638          *     this.dataY = [ A.Y(), A.Y()+d[0], mid[1], mid[1]+d[0], mid[1], B.Y()+d[0], B.Y() ];
639          * };
640          *
641          * // Text
642          * var txt = board.create('text', [
643          *                     function() {
644          *                         var d = [B.X()-A.X(), B.Y()-A.Y()],
645          *                             dl = Math.sqrt(d[0]*d[0]+d[1]*d[1]),
646          *                             mid = (A.X()+B.X())*0.5;
647          *
648          *                         d[1] *= height/dl;
649          *                         return mid-d[1]+0.1;
650          *                     },
651          *                     function() {
652          *                         var d = [B.X()-A.X(), B.Y()-A.Y()],
653          *                             dl = Math.sqrt(d[0]*d[0]+d[1]*d[1]),
654          *                             mid = (A.Y()+B.Y())*0.5;
655          *
656          *                         d[0] *= height/dl;
657          *                         return mid+d[0]+0.1;
658          *                     },
659          *                     function() { return "length=" + JXG.toFixed(B.Dist(A), 2); }
660          *                 ]);
661          *
662          *
663          * board.update(); // This update is necessary to call updateDataArray the first time.
664          *
665          * </pre><div id="JXGa61a4d66-e69f-11e5-b1bf-901b0e1b8723"  class="jxgbox" style="width: 300px; height: 300px;"></div>
666          * <script type="text/javascript">
667          *     (function() {
668          *      var board = JXG.JSXGraph.initBoard('JXGa61a4d66-e69f-11e5-b1bf-901b0e1b8723',
669          *             {boundingbox: [-4, 4, 4,-4], axis: true, showcopyright: false, shownavigation: false});
670          *     var A = board.create('point', [-3,3]);
671          *     var B = board.create('point', [3,-2]);
672          *     var line = board.create('segment', [A,B]);
673          *
674          *     var height = 0.5; // height of the curly brace
675          *
676          *     // Curly brace
677          *     var crl = board.create('curve', [[0],[0]], {strokeWidth:1, strokeColor:'black'});
678          *     crl.bezierDegree = 3;
679          *     crl.updateDataArray = function() {
680          *         var d = [B.X()-A.X(), B.Y()-A.Y()],
681          *             dl = Math.sqrt(d[0]*d[0]+d[1]*d[1]),
682          *             mid = [(A.X()+B.X())*0.5, (A.Y()+B.Y())*0.5];
683          *
684          *         d[0] *= height/dl;
685          *         d[1] *= height/dl;
686          *
687          *         this.dataX = [ A.X(), A.X()-d[1], mid[0], mid[0]-d[1], mid[0], B.X()-d[1], B.X() ];
688          *         this.dataY = [ A.Y(), A.Y()+d[0], mid[1], mid[1]+d[0], mid[1], B.Y()+d[0], B.Y() ];
689          *     };
690          *
691          *     // Text
692          *     var txt = board.create('text', [
693          *                         function() {
694          *                             var d = [B.X()-A.X(), B.Y()-A.Y()],
695          *                                 dl = Math.sqrt(d[0]*d[0]+d[1]*d[1]),
696          *                                 mid = (A.X()+B.X())*0.5;
697          *
698          *                             d[1] *= height/dl;
699          *                             return mid-d[1]+0.1;
700          *                         },
701          *                         function() {
702          *                             var d = [B.X()-A.X(), B.Y()-A.Y()],
703          *                                 dl = Math.sqrt(d[0]*d[0]+d[1]*d[1]),
704          *                                 mid = (A.Y()+B.Y())*0.5;
705          *
706          *                             d[0] *= height/dl;
707          *                             return mid+d[0]+0.1;
708          *                         },
709          *                         function() { return "length="+JXG.toFixed(B.Dist(A), 2); }
710          *                     ]);
711          *
712          *
713          *     board.update(); // This update is necessary to call updateDataArray the first time.
714          *
715          *     })();
716          *
717          * </script><pre>
718          *
719          *
720          */
721         updateDataArray: function () {
722             // this used to return this, but we shouldn't rely on the user to implement it.
723         },
724 
725         /**
726          * Computes the curve path
727          * @see JXG.Curve#update
728          * @returns {JXG.Curve} Reference to the curve object.
729          */
730         updateCurve: function () {
731             var i, len, mi, ma,
732                 x, y,
733                 version = this.visProp.plotversion,
734                 //t1, t2, l1,
735                 suspendUpdate = false;
736 
737             this.updateTransformMatrix();
738             this.updateDataArray();
739             mi = this.minX();
740             ma = this.maxX();
741 
742             // Discrete data points
743             // x-coordinates are in an array
744             if (Type.exists(this.dataX)) {
745                 this.numberPoints = this.dataX.length;
746                 len = this.numberPoints;
747 
748                 // It is possible, that the array length has increased.
749                 this.allocatePoints();
750 
751                 for (i = 0; i < len; i++) {
752                     x = i;
753 
754                     // y-coordinates are in an array
755                     if (Type.exists(this.dataY)) {
756                         y = i;
757                         // The last parameter prevents rounding in usr2screen().
758                         this.points[i].setCoordinates(
759                             Const.COORDS_BY_USER,
760                             [this.dataX[i], this.dataY[i]],
761                             false
762                         );
763                     } else {
764                         // discrete x data, continuous y data
765                         y = this.X(x);
766                         // The last parameter prevents rounding in usr2screen().
767                         this.points[i].setCoordinates(
768                             Const.COORDS_BY_USER,
769                             [this.dataX[i], this.Y(y, suspendUpdate)],
770                             false
771                         );
772                     }
773                     this.points[i]._t = i;
774 
775                     // this.updateTransform(this.points[i]);
776                     suspendUpdate = true;
777                 }
778                 // continuous x data
779             } else {
780                 if (this.evalVisProp('doadvancedplot')) {
781                     // console.time("plot");
782 
783                     if (version === 1 || this.evalVisProp('doadvancedplotold')) {
784                         Plot.updateParametricCurveOld(this, mi, ma);
785                     } else if (version === 2) {
786                         Plot.updateParametricCurve_v2(this, mi, ma);
787                     } else if (version === 3) {
788                         Plot.updateParametricCurve_v3(this, mi, ma);
789                     } else if (version === 4) {
790                         Plot.updateParametricCurve_v4(this, mi, ma);
791                     } else {
792                         Plot.updateParametricCurve_v2(this, mi, ma);
793                     }
794                     // console.timeEnd("plot");
795                 } else {
796                     if (this.board.updateQuality === this.board.BOARD_QUALITY_HIGH) {
797                         this.numberPoints = this.evalVisProp('numberpointshigh');
798                     } else {
799                         this.numberPoints = this.evalVisProp('numberpointslow');
800                     }
801 
802                     // It is possible, that the array length has increased.
803                     this.allocatePoints();
804                     Plot.updateParametricCurveNaive(this, mi, ma, this.numberPoints);
805                 }
806                 len = this.numberPoints;
807 
808                 if (
809                     this.evalVisProp('useqdt') &&
810                     this.board.updateQuality === this.board.BOARD_QUALITY_HIGH
811                 ) {
812                     this.qdt = new QDT(this.board.getBoundingBox());
813                     for (i = 0; i < this.points.length; i++) {
814                         this.qdt.insert(this.points[i]);
815 
816                         if (i > 0) {
817                             this.points[i].prev = this.points[i - 1];
818                         }
819 
820                         if (i < len - 1) {
821                             this.points[i].next = this.points[i + 1];
822                         }
823                     }
824                 }
825 
826                 // for (i = 0; i < len; i++) {
827                 //     this.updateTransform(this.points[i]);
828                 // }
829             }
830 
831             if (
832                 this.evalVisProp('curvetype') !== "plot" &&
833                 this.evalVisProp('rdpsmoothing')
834             ) {
835                 // console.time("rdp");
836                 this.points = Numerics.RamerDouglasPeucker(this.points, 0.2);
837                 this.numberPoints = this.points.length;
838                 // console.timeEnd("rdp");
839                 // console.log(this.numberPoints);
840             }
841 
842             len = this.numberPoints;
843             for (i = 0; i < len; i++) {
844                 this.updateTransform(this.points[i]);
845             }
846 
847             return this;
848         },
849 
850         updateTransformMatrix: function () {
851             var t,
852                 i,
853                 len = this.transformations.length;
854 
855             this.transformMat = [
856                 [1, 0, 0],
857                 [0, 1, 0],
858                 [0, 0, 1]
859             ];
860 
861             for (i = 0; i < len; i++) {
862                 t = this.transformations[i];
863                 t.update();
864                 this.transformMat = Mat.matMatMult(t.matrix, this.transformMat);
865             }
866 
867             return this;
868         },
869 
870         /**
871          * Applies the transformations of the curve to the given point <tt>p</tt>.
872          * Before using it, {@link JXG.Curve#updateTransformMatrix} has to be called.
873          * @param {JXG.Point} p
874          * @returns {JXG.Point} The given point.
875          */
876         updateTransform: function (p) {
877             var c,
878                 len = this.transformations.length;
879 
880             if (len > 0) {
881                 c = Mat.matVecMult(this.transformMat, p.usrCoords);
882                 p.setCoordinates(Const.COORDS_BY_USER, c, false, true);
883             }
884 
885             return p;
886         },
887 
888         /**
889          * Add transformations to this curve.
890          * @param {JXG.Transformation|Array} transform Either one {@link JXG.Transformation} or an array of {@link JXG.Transformation}s.
891          * @returns {JXG.Curve} Reference to the curve object.
892          */
893         addTransform: function (transform) {
894             var i,
895                 list = Type.isArray(transform) ? transform : [transform],
896                 len = list.length;
897 
898             for (i = 0; i < len; i++) {
899                 this.transformations.push(list[i]);
900             }
901 
902             return this;
903         },
904 
905         /**
906          * Generate the method curve.X() in case curve.dataX is an array
907          * and generate the method curve.Y() in case curve.dataY is an array.
908          * @private
909          * @param {String} which Either 'X' or 'Y'
910          * @returns {function}
911          **/
912         interpolationFunctionFromArray: function (which) {
913             var data = "data" + which,
914                 that = this;
915 
916             return function (t, suspendedUpdate) {
917                 var i,
918                     j,
919                     t0,
920                     t1,
921                     arr = that[data],
922                     len = arr.length,
923                     last,
924                     f = [];
925 
926                 if (isNaN(t)) {
927                     return NaN;
928                 }
929 
930                 if (t < 0) {
931                     if (Type.isFunction(arr[0])) {
932                         return arr[0]();
933                     }
934 
935                     return arr[0];
936                 }
937 
938                 if (that.bezierDegree === 3) {
939                     last = (len - 1) / 3;
940 
941                     if (t >= last) {
942                         if (Type.isFunction(arr[arr.length - 1])) {
943                             return arr[arr.length - 1]();
944                         }
945 
946                         return arr[arr.length - 1];
947                     }
948 
949                     i = Math.floor(t) * 3;
950                     t0 = t % 1;
951                     t1 = 1 - t0;
952 
953                     for (j = 0; j < 4; j++) {
954                         if (Type.isFunction(arr[i + j])) {
955                             f[j] = arr[i + j]();
956                         } else {
957                             f[j] = arr[i + j];
958                         }
959                     }
960 
961                     return (
962                         t1 * t1 * (t1 * f[0] + 3 * t0 * f[1]) +
963                         (3 * t1 * f[2] + t0 * f[3]) * t0 * t0
964                     );
965                 }
966 
967                 if (t > len - 2) {
968                     i = len - 2;
969                 } else {
970                     i = parseInt(Math.floor(t), 10);
971                 }
972 
973                 if (i === t) {
974                     if (Type.isFunction(arr[i])) {
975                         return arr[i]();
976                     }
977                     return arr[i];
978                 }
979 
980                 for (j = 0; j < 2; j++) {
981                     if (Type.isFunction(arr[i + j])) {
982                         f[j] = arr[i + j]();
983                     } else {
984                         f[j] = arr[i + j];
985                     }
986                 }
987                 return f[0] + (f[1] - f[0]) * (t - i);
988             };
989         },
990 
991         /**
992          * Converts the JavaScript/JessieCode/GEONExT syntax of the defining function term into JavaScript.
993          * New methods X() and Y() for the Curve object are generated, further
994          * new methods for minX() and maxX().
995          * If mi or ma are not supplied, default functions are set.
996          *
997          * @param {String} varname Name of the parameter in xterm and yterm, e.g. 'x' or 't'
998          * @param {String|Number|Function|Array} xterm Term for the x coordinate. Can also be an array consisting of discrete values.
999          * @param {String|Number|Function|Array} yterm Term for the y coordinate. Can also be an array consisting of discrete values.
1000          * @param {String|Number|Function} [mi] Lower bound on the parameter
1001          * @param {String|Number|Function} [ma] Upper bound on the parameter
1002          * @see JXG.GeonextParser.geonext2JS
1003          */
1004         generateTerm: function (varname, xterm, yterm, mi, ma) {
1005             var fx, fy;
1006 
1007             // Generate the methods X() and Y()
1008             if (Type.isArray(xterm)) {
1009                 // Discrete data
1010                 this.dataX = xterm;
1011 
1012                 this.numberPoints = this.dataX.length;
1013                 this.X = this.interpolationFunctionFromArray.apply(this, ["X"]);
1014                 this.visProp.curvetype = "plot";
1015                 this.isDraggable = true;
1016             } else {
1017                 // Continuous data
1018                 this.X = Type.createFunction(xterm, this.board, varname);
1019                 if (Type.isString(xterm)) {
1020                     this.visProp.curvetype = "functiongraph";
1021                 } else if (Type.isFunction(xterm) || Type.isNumber(xterm)) {
1022                     this.visProp.curvetype = "parameter";
1023                 }
1024 
1025                 this.isDraggable = true;
1026             }
1027 
1028             if (Type.isArray(yterm)) {
1029                 this.dataY = yterm;
1030                 this.Y = this.interpolationFunctionFromArray.apply(this, ["Y"]);
1031             } else {
1032                 this.Y = Type.createFunction(yterm, this.board, varname);
1033             }
1034 
1035             /**
1036              * Polar form
1037              * Input data is function xterm() and offset coordinates yterm
1038              */
1039             if (Type.isFunction(xterm) && Type.isArray(yterm)) {
1040                 // Xoffset, Yoffset
1041                 fx = Type.createFunction(yterm[0], this.board, "");
1042                 fy = Type.createFunction(yterm[1], this.board, "");
1043 
1044                 this.X = function (phi) {
1045                     return xterm(phi) * Math.cos(phi) + fx();
1046                 };
1047                 this.X.deps = fx.deps;
1048 
1049                 this.Y = function (phi) {
1050                     return xterm(phi) * Math.sin(phi) + fy();
1051                 };
1052                 this.Y.deps = fy.deps;
1053 
1054                 this.visProp.curvetype = "polar";
1055             }
1056 
1057             // Set the upper and lower bounds for the parameter of the curve.
1058             // If not defined, reset the bounds to the default values
1059             // given in Curve.prototype.minX, Curve.prototype.maxX
1060             if (Type.exists(mi)) {
1061                 this.minX = Type.createFunction(mi, this.board, "");
1062             } else {
1063                 delete this.minX;
1064             }
1065             if (Type.exists(ma)) {
1066                 this.maxX = Type.createFunction(ma, this.board, "");
1067             } else {
1068                 delete this.maxX;
1069             }
1070 
1071             this.addParentsFromJCFunctions([this.X, this.Y, this.minX, this.maxX]);
1072         },
1073 
1074         /**
1075          * Finds dependencies in a given term and notifies the parents by adding the
1076          * dependent object to the found objects child elements.
1077          * @param {String} contentStr String containing dependencies for the given object.
1078          */
1079         notifyParents: function (contentStr) {
1080             var fstr,
1081                 dep,
1082                 isJessieCode = false,
1083                 obj;
1084 
1085             // Read dependencies found by the JessieCode parser
1086             obj = { xterm: 1, yterm: 1 };
1087             for (fstr in obj) {
1088                 if (
1089                     obj.hasOwnProperty(fstr) &&
1090                     this.hasOwnProperty(fstr) &&
1091                     this[fstr].origin
1092                 ) {
1093                     isJessieCode = true;
1094                     for (dep in this[fstr].origin.deps) {
1095                         if (this[fstr].origin.deps.hasOwnProperty(dep)) {
1096                             this[fstr].origin.deps[dep].addChild(this);
1097                         }
1098                     }
1099                 }
1100             }
1101 
1102             if (!isJessieCode) {
1103                 GeonextParser.findDependencies(this, contentStr, this.board);
1104             }
1105         },
1106 
1107         // documented in geometry element
1108         getLabelAnchor: function () {
1109             var x, y, pos,
1110                 xy, lbda, e,
1111                 t, dx, dy, d,
1112                 dist = 1.5,
1113                 c,
1114                 ax = 0.05 * this.board.canvasWidth,
1115                 ay = 0.05 * this.board.canvasHeight,
1116                 bx = 0.95 * this.board.canvasWidth,
1117                 by = 0.95 * this.board.canvasHeight;
1118 
1119             if (!Type.exists(this.label)) {
1120                 return new Coords(Const.COORDS_BY_SCREEN, [NaN, NaN], this.board);
1121             }
1122             pos = this.label.evalVisProp('position');
1123             if (!Type.isString(pos)) {
1124                 return new Coords(Const.COORDS_BY_SCREEN, [NaN, NaN], this.board);
1125             }
1126 
1127             if (pos.indexOf('right') < 0 && pos.indexOf('left') < 0) {
1128                 switch (this.evalVisProp('label.position')) {
1129                     case "ulft":
1130                         x = ax;
1131                         y = ay;
1132                         break;
1133                     case "llft":
1134                         x = ax;
1135                         y = by;
1136                         break;
1137                     case "rt":
1138                         x = bx;
1139                         y = 0.5 * by;
1140                         break;
1141                     case "lrt":
1142                         x = bx;
1143                         y = by;
1144                         break;
1145                     case "urt":
1146                         x = bx;
1147                         y = ay;
1148                         break;
1149                     case "top":
1150                         x = 0.5 * bx;
1151                         y = ay;
1152                         break;
1153                     case "bot":
1154                         x = 0.5 * bx;
1155                         y = by;
1156                         break;
1157                     default:
1158                         // includes case 'lft'
1159                         x = ax;
1160                         y = 0.5 * by;
1161                 }
1162             } else {
1163                 // New positioning
1164                 xy = Type.parsePosition(pos);
1165                 lbda = Type.parseNumber(xy.pos, this.maxX() - this.minX(), 1);
1166 
1167                 if (xy.pos.indexOf('fr') < 0 &&
1168                     xy.pos.indexOf('%') < 0) {
1169                     // 'px' or numbers are not supported
1170                     lbda = 0;
1171                 }
1172 
1173                 t = this.minX() + lbda;
1174                 x = this.X(t);
1175                 y = this.Y(t);
1176                 c = (new Coords(Const.COORDS_BY_USER, [x, y], this.board)).scrCoords;
1177 
1178                 e = Mat.eps;
1179                 if (t < this.minX() + e) {
1180                     dx = (this.X(t + e) - this.X(t)) / e;
1181                     dy = (this.Y(t + e) - this.Y(t)) / e;
1182                 } else if (t > this.maxX() - e) {
1183                     dx = (this.X(t) - this.X(t - e)) / e;
1184                     dy = (this.Y(t) - this.Y(t - e)) / e;
1185                 } else {
1186                     dx = 0.5 * (this.X(t + e) - this.X(t - e)) / e;
1187                     dy = 0.5 * (this.Y(t + e) - this.Y(t - e)) / e;
1188                 }
1189                 d = Mat.hypot(dx, dy);
1190 
1191                 if (xy.side === 'left') {
1192                     dy *= -1;
1193                 } else {
1194                     dx *= -1;
1195                 }
1196 
1197                 // Position left or right
1198 
1199                 if (Type.exists(this.label)) {
1200                     dist = 0.5 * this.label.evalVisProp('distance') / d;
1201                 }
1202 
1203                 x = c[1] + dy * this.label.size[0] * dist;
1204                 y = c[2] - dx * this.label.size[1] * dist;
1205 
1206                 return new Coords(Const.COORDS_BY_SCREEN, [x, y], this.board);
1207 
1208             }
1209             c = new Coords(Const.COORDS_BY_SCREEN, [x, y], this.board, false);
1210             return Geometry.projectCoordsToCurve(
1211                 c.usrCoords[1], c.usrCoords[2], 0, this, this.board
1212             )[0];
1213         },
1214 
1215         // documented in geometry element
1216         cloneToBackground: function () {
1217             var er,
1218                 copy = Type.getCloneObject(this);
1219 
1220             copy.points = this.points.slice(0);
1221             copy.bezierDegree = this.bezierDegree;
1222             copy.numberPoints = this.numberPoints;
1223 
1224             er = this.board.renderer.enhancedRendering;
1225             this.board.renderer.enhancedRendering = true;
1226             this.board.renderer.drawCurve(copy);
1227             this.board.renderer.enhancedRendering = er;
1228             this.traces[copy.id] = copy.rendNode;
1229 
1230             return this;
1231         },
1232 
1233         // Already documented in GeometryElement
1234         bounds: function () {
1235             var minX = Infinity,
1236                 maxX = -Infinity,
1237                 minY = Infinity,
1238                 maxY = -Infinity,
1239                 l = this.points.length,
1240                 i,
1241                 bezier,
1242                 up;
1243 
1244             if (this.bezierDegree === 3) {
1245                 // Add methods X(), Y()
1246                 for (i = 0; i < l; i++) {
1247                     this.points[i].X = Type.bind(function () {
1248                         return this.usrCoords[1];
1249                     }, this.points[i]);
1250                     this.points[i].Y = Type.bind(function () {
1251                         return this.usrCoords[2];
1252                     }, this.points[i]);
1253                 }
1254                 bezier = Numerics.bezier(this.points);
1255                 up = bezier[3]();
1256                 minX = Numerics.fminbr(
1257                     function (t) {
1258                         return bezier[0](t);
1259                     },
1260                     [0, up]
1261                 );
1262                 maxX = Numerics.fminbr(
1263                     function (t) {
1264                         return -bezier[0](t);
1265                     },
1266                     [0, up]
1267                 );
1268                 minY = Numerics.fminbr(
1269                     function (t) {
1270                         return bezier[1](t);
1271                     },
1272                     [0, up]
1273                 );
1274                 maxY = Numerics.fminbr(
1275                     function (t) {
1276                         return -bezier[1](t);
1277                     },
1278                     [0, up]
1279                 );
1280 
1281                 minX = bezier[0](minX);
1282                 maxX = bezier[0](maxX);
1283                 minY = bezier[1](minY);
1284                 maxY = bezier[1](maxY);
1285                 return [minX, maxY, maxX, minY];
1286             }
1287 
1288             // Linear segments
1289             for (i = 0; i < l; i++) {
1290                 if (minX > this.points[i].usrCoords[1]) {
1291                     minX = this.points[i].usrCoords[1];
1292                 }
1293 
1294                 if (maxX < this.points[i].usrCoords[1]) {
1295                     maxX = this.points[i].usrCoords[1];
1296                 }
1297 
1298                 if (minY > this.points[i].usrCoords[2]) {
1299                     minY = this.points[i].usrCoords[2];
1300                 }
1301 
1302                 if (maxY < this.points[i].usrCoords[2]) {
1303                     maxY = this.points[i].usrCoords[2];
1304                 }
1305             }
1306 
1307             return [minX, maxY, maxX, minY];
1308         },
1309 
1310         // documented in element.js
1311         getParents: function () {
1312             var p = [this.xterm, this.yterm, this.minX(), this.maxX()];
1313 
1314             if (this.parents.length !== 0) {
1315                 p = this.parents;
1316             }
1317 
1318             return p;
1319         },
1320 
1321         /**
1322          * Shift the curve by the vector 'where'.
1323          *
1324          * @param {Array} where Array containing the x and y coordinate of the target location.
1325          * @returns {JXG.Curve} Reference to itself.
1326          */
1327         moveTo: function (where) {
1328             // TODO add animation
1329             var delta = [],
1330                 p;
1331             if (this.points.length > 0 && !this.evalVisProp('fixed')) {
1332                 p = this.points[0];
1333                 if (where.length === 3) {
1334                     delta = [
1335                         where[0] - p.usrCoords[0],
1336                         where[1] - p.usrCoords[1],
1337                         where[2] - p.usrCoords[2]
1338                     ];
1339                 } else {
1340                     delta = [where[0] - p.usrCoords[1], where[1] - p.usrCoords[2]];
1341                 }
1342                 this.setPosition(Const.COORDS_BY_USER, delta);
1343                 return this.board.update(this);
1344             }
1345             return this;
1346         },
1347 
1348         /**
1349          * If the curve is the result of a transformation applied
1350          * to a continuous curve, the glider projection has to be done
1351          * on the original curve. Otherwise there will be problems
1352          * when changing between high and low precision plotting,
1353          * since there number of points changes.
1354          *
1355          * @private
1356          * @returns {Array} [Boolean, curve]: Array contining 'true' if curve is result of a transformation,
1357          *   and the source curve of the transformation.
1358          */
1359         getTransformationSource: function () {
1360             var isTransformed, curve_org;
1361             if (Type.exists(this._transformationSource)) {
1362                 curve_org = this._transformationSource;
1363                 if (
1364                     curve_org.elementClass === Const.OBJECT_CLASS_CURVE //&&
1365                     //curve_org.evalVisProp('curvetype') !== 'plot'
1366                 ) {
1367                     isTransformed = true;
1368                 }
1369             }
1370             return [isTransformed, curve_org];
1371         }
1372 
1373         // See JXG.Math.Geometry.pnpoly
1374         // pnpoly: function (x_in, y_in, coord_type) {
1375         //     var i,
1376         //         j,
1377         //         len,
1378         //         x,
1379         //         y,
1380         //         crds,
1381         //         v = this.points,
1382         //         isIn = false;
1383 
1384         //     if (coord_type === Const.COORDS_BY_USER) {
1385         //         crds = new Coords(Const.COORDS_BY_USER, [x_in, y_in], this.board);
1386         //         x = crds.scrCoords[1];
1387         //         y = crds.scrCoords[2];
1388         //     } else {
1389         //         x = x_in;
1390         //         y = y_in;
1391         //     }
1392 
1393         //     len = this.points.length;
1394         //     for (i = 0, j = len - 2; i < len - 1; j = i++) {
1395         //         if (
1396         //             v[i].scrCoords[2] > y !== v[j].scrCoords[2] > y &&
1397         //             x <
1398         //                 ((v[j].scrCoords[1] - v[i].scrCoords[1]) * (y - v[i].scrCoords[2])) /
1399         //                     (v[j].scrCoords[2] - v[i].scrCoords[2]) +
1400         //                     v[i].scrCoords[1]
1401         //         ) {
1402         //             isIn = !isIn;
1403         //         }
1404         //     }
1405 
1406         //     return isIn;
1407         // }
1408     }
1409 );
1410 
1411 /**
1412  * @class  This element is used to provide a constructor for curve, which is just a wrapper for element {@link Curve}.
1413  * A curve is a mapping from R to R^2. t mapsto (x(t),y(t)). The graph is drawn for t in the interval [a,b].
1414  * <p>
1415  * The following types of curves can be plotted:
1416  * <ul>
1417  *  <li> parametric curves: t mapsto (x(t),y(t)), where x() and y() are univariate functions.
1418  *  <li> polar curves: curves commonly written with polar equations like spirals and cardioids.
1419  *  <li> data plots: plot line segments through a given list of coordinates.
1420  * </ul>
1421  * @pseudo
1422  * @name Curve
1423  * @augments JXG.Curve
1424  * @constructor
1425  * @type Object
1426  * @description JXG.Curve
1427 
1428  * @param {function,number_function,number_function,number_function,number}  x,y,a_,b_ Parent elements for Parametric Curves.
1429  *                     <p>
1430  *                     x describes the x-coordinate of the curve. It may be a function term in one variable, e.g. x(t).
1431  *                     In case of x being of type number, x(t) is set to  a constant function.
1432  *                     this function at the values of the array.
1433  *                     </p>
1434  *                     <p>
1435  *                     y describes the y-coordinate of the curve. In case of a number, y(t) is set to the constant function
1436  *                     returning this number.
1437  *                     </p>
1438  *                     <p>
1439  *                     Further parameters are an optional number or function for the left interval border a,
1440  *                     and an optional number or function for the right interval border b.
1441  *                     </p>
1442  *                     <p>
1443  *                     Default values are a=-10 and b=10.
1444  *                     </p>
1445  *
1446  * @param {array_array,function,number}
1447  *
1448  * @description x,y Parent elements for Data Plots.
1449  *                     <p>
1450  *                     x and y are arrays contining the x and y coordinates of the data points which are connected by
1451  *                     line segments. The individual entries of x and y may also be functions.
1452  *                     In case of x being an array the curve type is data plot, regardless of the second parameter and
1453  *                     if additionally the second parameter y is a function term the data plot evaluates.
1454  *                     </p>
1455  * @param {function_array,function,number_function,number_function,number}
1456  * @description r,offset_,a_,b_ Parent elements for Polar Curves.
1457  *                     <p>
1458  *                     The first parameter is a function term r(phi) describing the polar curve.
1459  *                     </p>
1460  *                     <p>
1461  *                     The second parameter is the offset of the curve. It has to be
1462  *                     an array containing numbers or functions describing the offset. Default value is the origin [0,0].
1463  *                     </p>
1464  *                     <p>
1465  *                     Further parameters are an optional number or function for the left interval border a,
1466  *                     and an optional number or function for the right interval border b.
1467  *                     </p>
1468  *                     <p>
1469  *                     Default values are a=-10 and b=10.
1470  *                     </p>
1471  * <p>
1472  * Additionally, a curve can be created by providing a curve and a transformation (or an array of transformations).
1473  * The result is a curve which is the transformation of the supplied curve.
1474  *
1475  * @see JXG.Curve
1476  * @example
1477  * // Parametric curve
1478  * // Create a curve of the form (t-sin(t), 1-cos(t), i.e.
1479  * // the cycloid curve.
1480  *   var graph = board.create('curve',
1481  *                        [function(t){ return t-Math.sin(t);},
1482  *                         function(t){ return 1-Math.cos(t);},
1483  *                         0, 2*Math.PI]
1484  *                     );
1485  * </pre><div class="jxgbox" id="JXGaf9f818b-f3b6-4c4d-8c4c-e4a4078b726d" style="width: 300px; height: 300px;"></div>
1486  * <script type="text/javascript">
1487  *   var c1_board = JXG.JSXGraph.initBoard('JXGaf9f818b-f3b6-4c4d-8c4c-e4a4078b726d', {boundingbox: [-1, 5, 7, -1], axis: true, showcopyright: false, shownavigation: false});
1488  *   var graph1 = c1_board.create('curve', [function(t){ return t-Math.sin(t);},function(t){ return 1-Math.cos(t);},0, 2*Math.PI]);
1489  * </script><pre>
1490  * @example
1491  * // Data plots
1492  * // Connect a set of points given by coordinates with dashed line segments.
1493  * // The x- and y-coordinates of the points are given in two separate
1494  * // arrays.
1495  *   var x = [0,1,2,3,4,5,6,7,8,9];
1496  *   var y = [9.2,1.3,7.2,-1.2,4.0,5.3,0.2,6.5,1.1,0.0];
1497  *   var graph = board.create('curve', [x,y], {dash:2});
1498  * </pre><div class="jxgbox" id="JXG7dcbb00e-b6ff-481d-b4a8-887f5d8c6a83" style="width: 300px; height: 300px;"></div>
1499  * <script type="text/javascript">
1500  *   var c3_board = JXG.JSXGraph.initBoard('JXG7dcbb00e-b6ff-481d-b4a8-887f5d8c6a83', {boundingbox: [-1,10,10,-1], axis: true, showcopyright: false, shownavigation: false});
1501  *   var x = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
1502  *   var y = [9.2, 1.3, 7.2, -1.2, 4.0, 5.3, 0.2, 6.5, 1.1, 0.0];
1503  *   var graph3 = c3_board.create('curve', [x,y], {dash:2});
1504  * </script><pre>
1505  * @example
1506  * // Polar plot
1507  * // Create a curve with the equation r(phi)= a*(1+phi), i.e.
1508  * // a cardioid.
1509  *   var a = board.create('slider',[[0,2],[2,2],[0,1,2]]);
1510  *   var graph = board.create('curve',
1511  *                        [function(phi){ return a.Value()*(1-Math.cos(phi));},
1512  *                         [1,0],
1513  *                         0, 2*Math.PI],
1514  *                         {curveType: 'polar'}
1515  *                     );
1516  * </pre><div class="jxgbox" id="JXGd0bc7a2a-8124-45ca-a6e7-142321a8f8c2" style="width: 300px; height: 300px;"></div>
1517  * <script type="text/javascript">
1518  *   var c2_board = JXG.JSXGraph.initBoard('JXGd0bc7a2a-8124-45ca-a6e7-142321a8f8c2', {boundingbox: [-3,3,3,-3], axis: true, showcopyright: false, shownavigation: false});
1519  *   var a = c2_board.create('slider',[[0,2],[2,2],[0,1,2]]);
1520  *   var graph2 = c2_board.create('curve', [function(phi){ return a.Value()*(1-Math.cos(phi));}, [1,0], 0, 2*Math.PI], {curveType: 'polar'});
1521  * </script><pre>
1522  *
1523  * @example
1524  *  // Draggable Bezier curve
1525  *  var col, p, c;
1526  *  col = 'blue';
1527  *  p = [];
1528  *  p.push(board.create('point',[-2, -1 ], {size: 5, strokeColor:col, fillColor:col}));
1529  *  p.push(board.create('point',[1, 2.5 ], {size: 5, strokeColor:col, fillColor:col}));
1530  *  p.push(board.create('point',[-1, -2.5 ], {size: 5, strokeColor:col, fillColor:col}));
1531  *  p.push(board.create('point',[2, -2], {size: 5, strokeColor:col, fillColor:col}));
1532  *
1533  *  c = board.create('curve', JXG.Math.Numerics.bezier(p),
1534  *              {strokeColor:'red', name:"curve", strokeWidth:5, fixed: false}); // Draggable curve
1535  *  c.addParents(p);
1536  * </pre><div class="jxgbox" id="JXG7bcc6280-f6eb-433e-8281-c837c3387849" style="width: 300px; height: 300px;"></div>
1537  * <script type="text/javascript">
1538  * (function(){
1539  *  var board, col, p, c;
1540  *  board = JXG.JSXGraph.initBoard('JXG7bcc6280-f6eb-433e-8281-c837c3387849', {boundingbox: [-3,3,3,-3], axis: true, showcopyright: false, shownavigation: false});
1541  *  col = 'blue';
1542  *  p = [];
1543  *  p.push(board.create('point',[-2, -1 ], {size: 5, strokeColor:col, fillColor:col}));
1544  *  p.push(board.create('point',[1, 2.5 ], {size: 5, strokeColor:col, fillColor:col}));
1545  *  p.push(board.create('point',[-1, -2.5 ], {size: 5, strokeColor:col, fillColor:col}));
1546  *  p.push(board.create('point',[2, -2], {size: 5, strokeColor:col, fillColor:col}));
1547  *
1548  *  c = board.create('curve', JXG.Math.Numerics.bezier(p),
1549  *              {strokeColor:'red', name:"curve", strokeWidth:5, fixed: false}); // Draggable curve
1550  *  c.addParents(p);
1551  * })();
1552  * </script><pre>
1553  *
1554  * @example
1555  *         // The curve cu2 is the reflection of cu1 against line li
1556  *         var li = board.create('line', [1,1,1], {strokeColor: '#aaaaaa'});
1557  *         var reflect = board.create('transform', [li], {type: 'reflect'});
1558  *         var cu1 = board.create('curve', [[-1, -1, -0.5, -1, -1, -0.5], [-3, -2, -2, -2, -2.5, -2.5]]);
1559  *         var cu2 = board.create('curve', [cu1, reflect], {strokeColor: 'red'});
1560  *
1561  * </pre><div id="JXG866dc7a2-d448-11e7-93b3-901b0e1b8723" class="jxgbox" style="width: 300px; height: 300px;"></div>
1562  * <script type="text/javascript">
1563  *     (function() {
1564  *         var board = JXG.JSXGraph.initBoard('JXG866dc7a2-d448-11e7-93b3-901b0e1b8723',
1565  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
1566  *             var li = board.create('line', [1,1,1], {strokeColor: '#aaaaaa'});
1567  *             var reflect = board.create('transform', [li], {type: 'reflect'});
1568  *             var cu1 = board.create('curve', [[-1, -1, -0.5, -1, -1, -0.5], [-3, -2, -2, -2, -2.5, -2.5]]);
1569  *             var cu2 = board.create('curve', [cu1, reflect], {strokeColor: 'red'});
1570  *
1571  *     })();
1572  *
1573  * </script><pre>
1574  */
1575 JXG.createCurve = function (board, parents, attributes) {
1576     var obj,
1577         cu,
1578         attr = Type.copyAttributes(attributes, board.options, "curve");
1579 
1580     obj = board.select(parents[0], true);
1581     if (
1582         Type.isTransformationOrArray(parents[1]) &&
1583         Type.isObject(obj) &&
1584         (obj.type === Const.OBJECT_TYPE_CURVE ||
1585             obj.type === Const.OBJECT_TYPE_ANGLE ||
1586             obj.type === Const.OBJECT_TYPE_ARC ||
1587             obj.type === Const.OBJECT_TYPE_CONIC ||
1588             obj.type === Const.OBJECT_TYPE_SECTOR)
1589     ) {
1590         if (obj.type === Const.OBJECT_TYPE_SECTOR) {
1591             attr = Type.copyAttributes(attributes, board.options, "sector");
1592         } else if (obj.type === Const.OBJECT_TYPE_ARC) {
1593             attr = Type.copyAttributes(attributes, board.options, "arc");
1594         } else if (obj.type === Const.OBJECT_TYPE_ANGLE) {
1595             if (!Type.exists(attributes.withLabel)) {
1596                 attributes.withLabel = false;
1597             }
1598             attr = Type.copyAttributes(attributes, board.options, "angle");
1599         } else {
1600             attr = Type.copyAttributes(attributes, board.options, "curve");
1601         }
1602         attr = Type.copyAttributes(attr, board.options, "curve");
1603 
1604         cu = new JXG.Curve(board, ["x", [], []], attr);
1605         /**
1606          * @class
1607          * @ignore
1608          */
1609         cu.updateDataArray = function () {
1610             var i,
1611                 le = obj.numberPoints;
1612             this.bezierDegree = obj.bezierDegree;
1613             this.dataX = [];
1614             this.dataY = [];
1615             for (i = 0; i < le; i++) {
1616                 this.dataX.push(obj.points[i].usrCoords[1]);
1617                 this.dataY.push(obj.points[i].usrCoords[2]);
1618             }
1619             return this;
1620         };
1621         cu.addTransform(parents[1]);
1622         obj.addChild(cu);
1623         cu.setParents([obj]);
1624         cu._transformationSource = obj;
1625 
1626         return cu;
1627     }
1628     attr = Type.copyAttributes(attributes, board.options, "curve");
1629     return new JXG.Curve(board, ["x"].concat(parents), attr);
1630 };
1631 
1632 JXG.registerElement("curve", JXG.createCurve);
1633 
1634 /**
1635  * @class This element is used to provide a constructor for functiongraph,
1636  * which is just a wrapper for element {@link Curve} with {@link JXG.Curve#X}()
1637  * set to x. The graph is drawn for x in the interval [a,b].
1638  * @pseudo
1639  * @name Functiongraph
1640  * @augments JXG.Curve
1641  * @constructor
1642  * @type JXG.Curve
1643  * @param {function_number,function_number,function} f,a_,b_ Parent elements are a function term f(x) describing the function graph.
1644  *         <p>
1645  *         Further, an optional number or function for the left interval border a,
1646  *         and an optional number or function for the right interval border b.
1647  *         <p>
1648  *         Default values are a=-10 and b=10.
1649  * @see JXG.Curve
1650  * @example
1651  * // Create a function graph for f(x) = 0.5*x*x-2*x
1652  *   var graph = board.create('functiongraph',
1653  *                        [function(x){ return 0.5*x*x-2*x;}, -2, 4]
1654  *                     );
1655  * </pre><div class="jxgbox" id="JXGefd432b5-23a3-4846-ac5b-b471e668b437" style="width: 300px; height: 300px;"></div>
1656  * <script type="text/javascript">
1657  *   var alex1_board = JXG.JSXGraph.initBoard('JXGefd432b5-23a3-4846-ac5b-b471e668b437', {boundingbox: [-3, 7, 5, -3], axis: true, showcopyright: false, shownavigation: false});
1658  *   var graph = alex1_board.create('functiongraph', [function(x){ return 0.5*x*x-2*x;}, -2, 4]);
1659  * </script><pre>
1660  * @example
1661  * // Create a function graph for f(x) = 0.5*x*x-2*x with variable interval
1662  *   var s = board.create('slider',[[0,4],[3,4],[-2,4,5]]);
1663  *   var graph = board.create('functiongraph',
1664  *                        [function(x){ return 0.5*x*x-2*x;},
1665  *                         -2,
1666  *                         function(){return s.Value();}]
1667  *                     );
1668  * </pre><div class="jxgbox" id="JXG4a203a84-bde5-4371-ad56-44619690bb50" style="width: 300px; height: 300px;"></div>
1669  * <script type="text/javascript">
1670  *   var alex2_board = JXG.JSXGraph.initBoard('JXG4a203a84-bde5-4371-ad56-44619690bb50', {boundingbox: [-3, 7, 5, -3], axis: true, showcopyright: false, shownavigation: false});
1671  *   var s = alex2_board.create('slider',[[0,4],[3,4],[-2,4,5]]);
1672  *   var graph = alex2_board.create('functiongraph', [function(x){ return 0.5*x*x-2*x;}, -2, function(){return s.Value();}]);
1673  * </script><pre>
1674  */
1675 JXG.createFunctiongraph = function (board, parents, attributes) {
1676     var attr,
1677         par = ["x", "x"].concat(parents); // variable name and identity function for x-coordinate
1678     // par = ["x", function(x) { return x; }].concat(parents);
1679 
1680     attr = Type.copyAttributes(attributes, board.options, "functiongraph");
1681     attr = Type.copyAttributes(attr, board.options, "curve");
1682     attr.curvetype = "functiongraph";
1683     return new JXG.Curve(board, par, attr);
1684 };
1685 
1686 JXG.registerElement("functiongraph", JXG.createFunctiongraph);
1687 JXG.registerElement("plot", JXG.createFunctiongraph);
1688 
1689 /**
1690  * @class This element is used to provide a constructor for (natural) cubic spline curves.
1691  * Create a dynamic spline interpolated curve given by sample points p_1 to p_n.
1692  * @pseudo
1693  * @name Spline
1694  * @augments JXG.Curve
1695  * @constructor
1696  * @type JXG.Curve
1697  * @param {JXG.Board} board Reference to the board the spline is drawn on.
1698  * @param {Array} parents Array of points the spline interpolates. This can be
1699  *   <ul>
1700  *   <li> an array of JSXGraph points</li>
1701  *   <li> an array of coordinate pairs</li>
1702  *   <li> an array of functions returning coordinate pairs</li>
1703  *   <li> an array consisting of an array with x-coordinates and an array of y-coordinates</li>
1704  *   </ul>
1705  *   All individual entries of coordinates arrays may be numbers or functions returning numbers.
1706  * @param {Object} attributes Define color, width, ... of the spline
1707  * @returns {JXG.Curve} Returns reference to an object of type JXG.Curve.
1708  * @see JXG.Curve
1709  * @example
1710  *
1711  * var p = [];
1712  * p[0] = board.create('point', [-2,2], {size: 4, face: 'o'});
1713  * p[1] = board.create('point', [0,-1], {size: 4, face: 'o'});
1714  * p[2] = board.create('point', [2,0], {size: 4, face: 'o'});
1715  * p[3] = board.create('point', [4,1], {size: 4, face: 'o'});
1716  *
1717  * var c = board.create('spline', p, {strokeWidth:3});
1718  * </pre><div id="JXG6c197afc-e482-11e5-b1bf-901b0e1b8723" style="width: 300px; height: 300px;"></div>
1719  * <script type="text/javascript">
1720  *     (function() {
1721  *         var board = JXG.JSXGraph.initBoard('JXG6c197afc-e482-11e5-b1bf-901b0e1b8723',
1722  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
1723  *
1724  *     var p = [];
1725  *     p[0] = board.create('point', [-2,2], {size: 4, face: 'o'});
1726  *     p[1] = board.create('point', [0,-1], {size: 4, face: 'o'});
1727  *     p[2] = board.create('point', [2,0], {size: 4, face: 'o'});
1728  *     p[3] = board.create('point', [4,1], {size: 4, face: 'o'});
1729  *
1730  *     var c = board.create('spline', p, {strokeWidth:3});
1731  *     })();
1732  *
1733  * </script><pre>
1734  *
1735  */
1736 JXG.createSpline = function (board, parents, attributes) {
1737     var el, funcs, ret;
1738 
1739     funcs = function () {
1740         var D,
1741             x = [],
1742             y = [];
1743 
1744         return [
1745             function (t, suspended) {
1746                 // Function term
1747                 var i, j, c;
1748 
1749                 if (!suspended) {
1750                     x = [];
1751                     y = [];
1752 
1753                     // given as [x[], y[]]
1754                     if (
1755                         parents.length === 2 &&
1756                         Type.isArray(parents[0]) &&
1757                         Type.isArray(parents[1]) &&
1758                         parents[0].length === parents[1].length
1759                     ) {
1760                         for (i = 0; i < parents[0].length; i++) {
1761                             if (Type.isFunction(parents[0][i])) {
1762                                 x.push(parents[0][i]());
1763                             } else {
1764                                 x.push(parents[0][i]);
1765                             }
1766 
1767                             if (Type.isFunction(parents[1][i])) {
1768                                 y.push(parents[1][i]());
1769                             } else {
1770                                 y.push(parents[1][i]);
1771                             }
1772                         }
1773                     } else {
1774                         for (i = 0; i < parents.length; i++) {
1775                             if (Type.isPoint(parents[i])) {
1776                                 x.push(parents[i].X());
1777                                 y.push(parents[i].Y());
1778                                 // given as [[x1,y1], [x2, y2], ...]
1779                             } else if (Type.isArray(parents[i]) && parents[i].length === 2) {
1780                                 for (j = 0; j < parents.length; j++) {
1781                                     if (Type.isFunction(parents[j][0])) {
1782                                         x.push(parents[j][0]());
1783                                     } else {
1784                                         x.push(parents[j][0]);
1785                                     }
1786 
1787                                     if (Type.isFunction(parents[j][1])) {
1788                                         y.push(parents[j][1]());
1789                                     } else {
1790                                         y.push(parents[j][1]);
1791                                     }
1792                                 }
1793                             } else if (
1794                                 Type.isFunction(parents[i]) &&
1795                                 parents[i]().length === 2
1796                             ) {
1797                                 c = parents[i]();
1798                                 x.push(c[0]);
1799                                 y.push(c[1]);
1800                             }
1801                         }
1802                     }
1803 
1804                     // The array D has only to be calculated when the position of one or more sample points
1805                     // changes. Otherwise D is always the same for all points on the spline.
1806                     D = Numerics.splineDef(x, y);
1807                 }
1808 
1809                 return Numerics.splineEval(t, x, y, D);
1810             },
1811             // minX()
1812             function () {
1813                 return x[0];
1814             },
1815             //maxX()
1816             function () {
1817                 return x[x.length - 1];
1818             }
1819         ];
1820     };
1821 
1822     attributes = Type.copyAttributes(attributes, board.options, "curve");
1823     attributes.curvetype = "functiongraph";
1824     ret = funcs();
1825     el = new JXG.Curve(board, ["x", "x", ret[0], ret[1], ret[2]], attributes);
1826     el.setParents(parents);
1827     el.elType = "spline";
1828 
1829     return el;
1830 };
1831 
1832 /**
1833  * Register the element type spline at JSXGraph
1834  * @private
1835  */
1836 JXG.registerElement("spline", JXG.createSpline);
1837 
1838 /**
1839  * @class This element is used to provide a constructor for cardinal spline curves.
1840  * Create a dynamic cardinal spline interpolated curve given by sample points p_1 to p_n.
1841  * @pseudo
1842  * @name Cardinalspline
1843  * @augments JXG.Curve
1844  * @constructor
1845  * @type JXG.Curve
1846  * @param {JXG.Board} board Reference to the board the cardinal spline is drawn on.
1847  * @param {Array} parents Array with three entries.
1848  * <p>
1849  *   First entry: Array of points the spline interpolates. This can be
1850  *   <ul>
1851  *   <li> an array of JSXGraph points</li>
1852  *   <li> an array of coordinate pairs</li>
1853  *   <li> an array of functions returning coordinate pairs</li>
1854  *   <li> an array consisting of an array with x-coordinates and an array of y-coordinates</li>
1855  *   </ul>
1856  *   All individual entries of coordinates arrays may be numbers or functions returning numbers.
1857  *   <p>
1858  *   Second entry: tau number or function
1859  *   <p>
1860  *   Third entry: type string containing 'uniform' (default) or 'centripetal'.
1861  * @param {Object} attributes Define color, width, ... of the cardinal spline
1862  * @returns {JXG.Curve} Returns reference to an object of type JXG.Curve.
1863  * @see JXG.Curve
1864  * @example
1865  * //create a cardinal spline out of an array of JXG points with adjustable tension
1866  * //create array of points
1867  * var p1 = board.create('point',[0,0])
1868  * var p2 = board.create('point',[1,4])
1869  * var p3 = board.create('point',[4,5])
1870  * var p4 = board.create('point',[2,3])
1871  * var p5 = board.create('point',[3,0])
1872  * var p = [p1,p2,p3,p4,p5]
1873  *
1874  * // tension
1875  * tau = board.create('slider', [[4,3],[9,3],[0.001,0.5,1]], {name:'tau'});
1876  * c = board.create('curve', JXG.Math.Numerics.CardinalSpline(p, function(){ return tau.Value();}), {strokeWidth:3});
1877  * </pre><div id="JXG6c197afc-e482-11e5-b2af-901b0e1b8723" style="width: 300px; height: 300px;"></div>
1878  * <script type="text/javascript">
1879  *     (function() {
1880  *         var board = JXG.JSXGraph.initBoard('JXG6c197afc-e482-11e5-b2af-901b0e1b8723',
1881  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
1882  *
1883  *     var p = [];
1884  *     p[0] = board.create('point', [-2,2], {size: 4, face: 'o'});
1885  *     p[1] = board.create('point', [0,-1], {size: 4, face: 'o'});
1886  *     p[2] = board.create('point', [2,0], {size: 4, face: 'o'});
1887  *     p[3] = board.create('point', [4,1], {size: 4, face: 'o'});
1888  *
1889  *     var c = board.create('spline', p, {strokeWidth:3});
1890  *     })();
1891  *
1892  * </script><pre>
1893  */
1894 JXG.createCardinalSpline = function (board, parents, attributes) {
1895     var el,
1896         getPointLike,
1897         points,
1898         tau,
1899         type,
1900         p,
1901         q,
1902         i,
1903         le,
1904         splineArr,
1905         errStr = "\nPossible parent types: [points:array, tau:number|function, type:string]";
1906 
1907     if (!Type.exists(parents[0]) || !Type.isArray(parents[0])) {
1908         throw new Error(
1909             "JSXGraph: JXG.createCardinalSpline: argument 1 'points' has to be array of points or coordinate pairs" +
1910             errStr
1911         );
1912     }
1913     if (
1914         !Type.exists(parents[1]) ||
1915         (!Type.isNumber(parents[1]) && !Type.isFunction(parents[1]))
1916     ) {
1917         throw new Error(
1918             "JSXGraph: JXG.createCardinalSpline: argument 2 'tau' has to be number between [0,1] or function'" +
1919             errStr
1920         );
1921     }
1922     if (!Type.exists(parents[2]) || !Type.isString(parents[2])) {
1923         throw new Error(
1924             "JSXGraph: JXG.createCardinalSpline: argument 3 'type' has to be string 'uniform' or 'centripetal'" +
1925             errStr
1926         );
1927     }
1928 
1929     attributes = Type.copyAttributes(attributes, board.options, "curve");
1930     attributes = Type.copyAttributes(attributes, board.options, "cardinalspline");
1931     attributes.curvetype = "parameter";
1932 
1933     p = parents[0];
1934     q = [];
1935 
1936     // Given as [x[], y[]]
1937     if (
1938         !attributes.isarrayofcoordinates &&
1939         p.length === 2 &&
1940         Type.isArray(p[0]) &&
1941         Type.isArray(p[1]) &&
1942         p[0].length === p[1].length
1943     ) {
1944         for (i = 0; i < p[0].length; i++) {
1945             q[i] = [];
1946             if (Type.isFunction(p[0][i])) {
1947                 q[i].push(p[0][i]());
1948             } else {
1949                 q[i].push(p[0][i]);
1950             }
1951 
1952             if (Type.isFunction(p[1][i])) {
1953                 q[i].push(p[1][i]());
1954             } else {
1955                 q[i].push(p[1][i]);
1956             }
1957         }
1958     } else {
1959         // given as [[x0, y0], [x1, y1], point, ...]
1960         for (i = 0; i < p.length; i++) {
1961             if (Type.isString(p[i])) {
1962                 q.push(board.select(p[i]));
1963             } else if (Type.isPoint(p[i])) {
1964                 q.push(p[i]);
1965                 // given as [[x0,y0], [x1, y2], ...]
1966             } else if (Type.isArray(p[i]) && p[i].length === 2) {
1967                 q[i] = [];
1968                 if (Type.isFunction(p[i][0])) {
1969                     q[i].push(p[i][0]());
1970                 } else {
1971                     q[i].push(p[i][0]);
1972                 }
1973 
1974                 if (Type.isFunction(p[i][1])) {
1975                     q[i].push(p[i][1]());
1976                 } else {
1977                     q[i].push(p[i][1]);
1978                 }
1979             } else if (Type.isFunction(p[i]) && p[i]().length === 2) {
1980                 q.push(parents[i]());
1981             }
1982         }
1983     }
1984 
1985     if (attributes.createpoints === true) {
1986         points = Type.providePoints(board, q, attributes, "cardinalspline", ["points"]);
1987     } else {
1988         points = [];
1989 
1990         /**
1991          * @ignore
1992          */
1993         getPointLike = function (ii) {
1994             return {
1995                 X: function () {
1996                     return q[ii][0];
1997                 },
1998                 Y: function () {
1999                     return q[ii][1];
2000                 },
2001                 Dist: function (p) {
2002                     var dx = this.X() - p.X(),
2003                         dy = this.Y() - p.Y();
2004 
2005                     return Mat.hypot(dx, dy);
2006                 }
2007             };
2008         };
2009 
2010         for (i = 0; i < q.length; i++) {
2011             if (Type.isPoint(q[i])) {
2012                 points.push(q[i]);
2013             } else {
2014                 points.push(getPointLike(i));
2015             }
2016         }
2017     }
2018 
2019     tau = parents[1];
2020     type = parents[2];
2021 
2022     splineArr = ["x"].concat(Numerics.CardinalSpline(points, tau, type));
2023 
2024     el = new JXG.Curve(board, splineArr, attributes);
2025     le = points.length;
2026     el.setParents(points);
2027     for (i = 0; i < le; i++) {
2028         p = points[i];
2029         if (Type.isPoint(p)) {
2030             if (Type.exists(p._is_new)) {
2031                 el.addChild(p);
2032                 delete p._is_new;
2033             } else {
2034                 p.addChild(el);
2035             }
2036         }
2037     }
2038     el.elType = "cardinalspline";
2039 
2040     return el;
2041 };
2042 
2043 /**
2044  * Register the element type cardinalspline at JSXGraph
2045  * @private
2046  */
2047 JXG.registerElement("cardinalspline", JXG.createCardinalSpline);
2048 
2049 /**
2050  * @class This element is used to provide a constructor for metapost spline curves.
2051  * Create a dynamic metapost spline interpolated curve given by sample points p_1 to p_n.
2052  * @pseudo
2053  * @name Metapostspline
2054  * @augments JXG.Curve
2055  * @constructor
2056  * @type JXG.Curve
2057  * @param {JXG.Board} board Reference to the board the metapost spline is drawn on.
2058  * @param {Array} parents Array with two entries.
2059  * <p>
2060  *   First entry: Array of points the spline interpolates. This can be
2061  *   <ul>
2062  *   <li> an array of JSXGraph points</li>
2063  *   <li> an object of coordinate pairs</li>
2064  *   <li> an array of functions returning coordinate pairs</li>
2065  *   <li> an array consisting of an array with x-coordinates and an array of y-coordinates</li>
2066  *   </ul>
2067  *   All individual entries of coordinates arrays may be numbers or functions returning numbers.
2068  *   <p>
2069  *   Second entry: JavaScript object containing the control values like tension, direction, curl.
2070  * @param {Object} attributes Define color, width, ... of the metapost spline
2071  * @returns {JXG.Curve} Returns reference to an object of type JXG.Curve.
2072  * @see JXG.Curve
2073  * @example
2074  *     var po = [],
2075  *         attr = {
2076  *             size: 5,
2077  *             color: 'red'
2078  *         },
2079  *         controls;
2080  *
2081  *     var tension = board.create('slider', [[-3, 6], [3, 6], [0, 1, 20]], {name: 'tension'});
2082  *     var curl = board.create('slider', [[-3, 5], [3, 5], [0, 1, 30]], {name: 'curl A, D'});
2083  *     var dir = board.create('slider', [[-3, 4], [3, 4], [-180, 0, 180]], {name: 'direction B'});
2084  *
2085  *     po.push(board.create('point', [-3, -3]));
2086  *     po.push(board.create('point', [0, -3]));
2087  *     po.push(board.create('point', [4, -5]));
2088  *     po.push(board.create('point', [6, -2]));
2089  *
2090  *     var controls = {
2091  *         tension: function() {return tension.Value(); },
2092  *         direction: { 1: function() {return dir.Value(); } },
2093  *         curl: { 0: function() {return curl.Value(); },
2094  *                 3: function() {return curl.Value(); }
2095  *             },
2096  *         isClosed: false
2097  *     };
2098  *
2099  *     // Plot a metapost curve
2100  *     var cu = board.create('metapostspline', [po, controls], {strokeColor: 'blue', strokeWidth: 2});
2101  *
2102  *
2103  * </pre><div id="JXGb8c6ffed-7419-41a3-9e55-3754b2327ae9" class="jxgbox" style="width: 300px; height: 300px;"></div>
2104  * <script type="text/javascript">
2105  *     (function() {
2106  *         var board = JXG.JSXGraph.initBoard('JXGb8c6ffed-7419-41a3-9e55-3754b2327ae9',
2107  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
2108  *         var po = [],
2109  *             attr = {
2110  *                 size: 5,
2111  *                 color: 'red'
2112  *             },
2113  *             controls;
2114  *
2115  *         var tension = board.create('slider', [[-3, 6], [3, 6], [0, 1, 20]], {name: 'tension'});
2116  *         var curl = board.create('slider', [[-3, 5], [3, 5], [0, 1, 30]], {name: 'curl A, D'});
2117  *         var dir = board.create('slider', [[-3, 4], [3, 4], [-180, 0, 180]], {name: 'direction B'});
2118  *
2119  *         po.push(board.create('point', [-3, -3]));
2120  *         po.push(board.create('point', [0, -3]));
2121  *         po.push(board.create('point', [4, -5]));
2122  *         po.push(board.create('point', [6, -2]));
2123  *
2124  *         var controls = {
2125  *             tension: function() {return tension.Value(); },
2126  *             direction: { 1: function() {return dir.Value(); } },
2127  *             curl: { 0: function() {return curl.Value(); },
2128  *                     3: function() {return curl.Value(); }
2129  *                 },
2130  *             isClosed: false
2131  *         };
2132  *
2133  *         // Plot a metapost curve
2134  *         var cu = board.create('metapostspline', [po, controls], {strokeColor: 'blue', strokeWidth: 2});
2135  *
2136  *
2137  *     })();
2138  *
2139  * </script><pre>
2140  *
2141  */
2142 JXG.createMetapostSpline = function (board, parents, attributes) {
2143     var el,
2144         getPointLike,
2145         points,
2146         controls,
2147         p,
2148         q,
2149         i,
2150         le,
2151         errStr = "\nPossible parent types: [points:array, controls:object";
2152 
2153     if (!Type.exists(parents[0]) || !Type.isArray(parents[0])) {
2154         throw new Error(
2155             "JSXGraph: JXG.createMetapostSpline: argument 1 'points' has to be array of points or coordinate pairs" +
2156             errStr
2157         );
2158     }
2159     if (!Type.exists(parents[1]) || !Type.isObject(parents[1])) {
2160         throw new Error(
2161             "JSXGraph: JXG.createMetapostSpline: argument 2 'controls' has to be a JavaScript object'" +
2162             errStr
2163         );
2164     }
2165 
2166     attributes = Type.copyAttributes(attributes, board.options, "curve");
2167     attributes = Type.copyAttributes(attributes, board.options, "metapostspline");
2168     attributes.curvetype = "parameter";
2169 
2170     p = parents[0];
2171     q = [];
2172 
2173     // given as [x[], y[]]
2174     if (
2175         !attributes.isarrayofcoordinates &&
2176         p.length === 2 &&
2177         Type.isArray(p[0]) &&
2178         Type.isArray(p[1]) &&
2179         p[0].length === p[1].length
2180     ) {
2181         for (i = 0; i < p[0].length; i++) {
2182             q[i] = [];
2183             if (Type.isFunction(p[0][i])) {
2184                 q[i].push(p[0][i]());
2185             } else {
2186                 q[i].push(p[0][i]);
2187             }
2188 
2189             if (Type.isFunction(p[1][i])) {
2190                 q[i].push(p[1][i]());
2191             } else {
2192                 q[i].push(p[1][i]);
2193             }
2194         }
2195     } else {
2196         // given as [[x0, y0], [x1, y1], point, ...]
2197         for (i = 0; i < p.length; i++) {
2198             if (Type.isString(p[i])) {
2199                 q.push(board.select(p[i]));
2200             } else if (Type.isPoint(p[i])) {
2201                 q.push(p[i]);
2202                 // given as [[x0,y0], [x1, y2], ...]
2203             } else if (Type.isArray(p[i]) && p[i].length === 2) {
2204                 q[i] = [];
2205                 if (Type.isFunction(p[i][0])) {
2206                     q[i].push(p[i][0]());
2207                 } else {
2208                     q[i].push(p[i][0]);
2209                 }
2210 
2211                 if (Type.isFunction(p[i][1])) {
2212                     q[i].push(p[i][1]());
2213                 } else {
2214                     q[i].push(p[i][1]);
2215                 }
2216             } else if (Type.isFunction(p[i]) && p[i]().length === 2) {
2217                 q.push(parents[i]());
2218             }
2219         }
2220     }
2221 
2222     if (attributes.createpoints === true) {
2223         points = Type.providePoints(board, q, attributes, 'metapostspline', ['points']);
2224     } else {
2225         points = [];
2226 
2227         /**
2228          * @ignore
2229          */
2230         getPointLike = function (ii) {
2231             return {
2232                 X: function () {
2233                     return q[ii][0];
2234                 },
2235                 Y: function () {
2236                     return q[ii][1];
2237                 }
2238             };
2239         };
2240 
2241         for (i = 0; i < q.length; i++) {
2242             if (Type.isPoint(q[i])) {
2243                 points.push(q[i]);
2244             } else {
2245                 points.push(getPointLike);
2246             }
2247         }
2248     }
2249 
2250     controls = parents[1];
2251 
2252     el = new JXG.Curve(board, ["t", [], [], 0, p.length - 1], attributes);
2253     /**
2254      * @class
2255      * @ignore
2256      */
2257     el.updateDataArray = function () {
2258         var res,
2259             i,
2260             len = points.length,
2261             p = [];
2262 
2263         for (i = 0; i < len; i++) {
2264             p.push([points[i].X(), points[i].Y()]);
2265         }
2266 
2267         res = Metapost.curve(p, controls);
2268         this.dataX = res[0];
2269         this.dataY = res[1];
2270     };
2271     el.bezierDegree = 3;
2272 
2273     le = points.length;
2274     el.setParents(points);
2275     for (i = 0; i < le; i++) {
2276         if (Type.isPoint(points[i])) {
2277             points[i].addChild(el);
2278         }
2279     }
2280     el.elType = "metapostspline";
2281 
2282     return el;
2283 };
2284 
2285 JXG.registerElement("metapostspline", JXG.createMetapostSpline);
2286 
2287 /**
2288  * @class This element is used to provide a constructor for Riemann sums, which is realized as a special curve.
2289  * The returned element has the method Value() which returns the sum of the areas of the bars.
2290  * <p>
2291  * In case of type "simpson" and "trapezoidal", the horizontal line approximating the function value
2292  * is replaced by a parabola or a secant. IN case of "simpson",
2293  * the parabola is approximated visually by a polygonal chain of fixed step width.
2294  *
2295  * @pseudo
2296  * @name Riemannsum
2297  * @augments JXG.Curve
2298  * @constructor
2299  * @type Curve
2300  * @param {function,array_number,function_string,function_function,number_function,number} f,n,type_,a_,b_ Parent elements of Riemannsum are a
2301  *         Either a function term f(x) describing the function graph which is filled by the Riemann bars, or
2302  *         an array consisting of two functions and the area between is filled by the Riemann bars.
2303  *         <p>
2304  *         n determines the number of bars, it is either a fixed number or a function.
2305  *         <p>
2306  *         type is a string or function returning one of the values:  'left', 'right', 'middle', 'lower', 'upper', 'random', 'simpson', or 'trapezoidal'.
2307  *         Default value is 'left'. "simpson" is Simpson's 1/3 rule.
2308  *         <p>
2309  *         Further parameters are an optional number or function for the left interval border a,
2310  *         and an optional number or function for the right interval border b.
2311  *         <p>
2312  *         Default values are a=-10 and b=10.
2313  * @see JXG.Curve
2314  * @example
2315  * // Create Riemann sums for f(x) = 0.5*x*x-2*x.
2316  *   var s = board.create('slider',[[0,4],[3,4],[0,4,10]],{snapWidth:1});
2317  *   var f = function(x) { return 0.5*x*x-2*x; };
2318  *   var r = board.create('riemannsum',
2319  *               [f, function(){return s.Value();}, 'upper', -2, 5],
2320  *               {fillOpacity:0.4}
2321  *               );
2322  *   var g = board.create('functiongraph',[f, -2, 5]);
2323  *   var t = board.create('text',[-2,-2, function(){ return 'Sum=' + JXG.toFixed(r.Value(), 4); }]);
2324  * </pre><div class="jxgbox" id="JXG940f40cc-2015-420d-9191-c5d83de988cf" style="width: 300px; height: 300px;"></div>
2325  * <script type="text/javascript">
2326  * (function(){
2327  *   var board = JXG.JSXGraph.initBoard('JXG940f40cc-2015-420d-9191-c5d83de988cf', {boundingbox: [-3, 7, 5, -3], axis: true, showcopyright: false, shownavigation: false});
2328  *   var f = function(x) { return 0.5*x*x-2*x; };
2329  *   var s = board.create('slider',[[0,4],[3,4],[0,4,10]],{snapWidth:1});
2330  *   var r = board.create('riemannsum', [f, function(){return s.Value();}, 'upper', -2, 5], {fillOpacity:0.4});
2331  *   var g = board.create('functiongraph', [f, -2, 5]);
2332  *   var t = board.create('text',[-2,-2, function(){ return 'Sum=' + JXG.toFixed(r.Value(), 4); }]);
2333  * })();
2334  * </script><pre>
2335  *
2336  * @example
2337  *   // Riemann sum between two functions
2338  *   var s = board.create('slider',[[0,4],[3,4],[0,4,10]],{snapWidth:1});
2339  *   var g = function(x) { return 0.5*x*x-2*x; };
2340  *   var f = function(x) { return -x*(x-4); };
2341  *   var r = board.create('riemannsum',
2342  *               [[g,f], function(){return s.Value();}, 'lower', 0, 4],
2343  *               {fillOpacity:0.4}
2344  *               );
2345  *   var f = board.create('functiongraph',[f, -2, 5]);
2346  *   var g = board.create('functiongraph',[g, -2, 5]);
2347  *   var t = board.create('text',[-2,-2, function(){ return 'Sum=' + JXG.toFixed(r.Value(), 4); }]);
2348  * </pre><div class="jxgbox" id="JXGf9a7ba38-b50f-4a32-a873-2f3bf9caee79" style="width: 300px; height: 300px;"></div>
2349  * <script type="text/javascript">
2350  * (function(){
2351  *   var board = JXG.JSXGraph.initBoard('JXGf9a7ba38-b50f-4a32-a873-2f3bf9caee79', {boundingbox: [-3, 7, 5, -3], axis: true, showcopyright: false, shownavigation: false});
2352  *   var s = board.create('slider',[[0,4],[3,4],[0,4,10]],{snapWidth:1});
2353  *   var g = function(x) { return 0.5*x*x-2*x; };
2354  *   var f = function(x) { return -x*(x-4); };
2355  *   var r = board.create('riemannsum',
2356  *               [[g,f], function(){return s.Value();}, 'lower', 0, 4],
2357  *               {fillOpacity:0.4}
2358  *               );
2359  *   var f = board.create('functiongraph',[f, -2, 5]);
2360  *   var g = board.create('functiongraph',[g, -2, 5]);
2361  *   var t = board.create('text',[-2,-2, function(){ return 'Sum=' + JXG.toFixed(r.Value(), 4); }]);
2362  * })();
2363  * </script><pre>
2364  */
2365 JXG.createRiemannsum = function (board, parents, attributes) {
2366     var n, type, f, par, c, attr;
2367 
2368     attr = Type.copyAttributes(attributes, board.options, "riemannsum");
2369     attr.curvetype = "plot";
2370 
2371     f = parents[0];
2372     n = Type.createFunction(parents[1], board, "");
2373 
2374     if (!Type.exists(n)) {
2375         throw new Error(
2376             "JSXGraph: JXG.createRiemannsum: argument '2' n has to be number or function." +
2377             "\nPossible parent types: [function,n:number|function,type,start:number|function,end:number|function]"
2378         );
2379     }
2380 
2381     if (typeof parents[2] === 'string') {
2382         parents[2] = '\'' + parents[2] + '\'';
2383     }
2384 
2385     type = Type.createFunction(parents[2], board, "");
2386     if (!Type.exists(type)) {
2387         throw new Error(
2388             "JSXGraph: JXG.createRiemannsum: argument 3 'type' has to be string or function." +
2389             "\nPossible parent types: [function,n:number|function,type,start:number|function,end:number|function]"
2390         );
2391     }
2392 
2393     par = [[0], [0]].concat(parents.slice(3));
2394 
2395     c = board.create("curve", par, attr);
2396 
2397     c.sum = 0.0;
2398     /**
2399      * Returns the value of the Riemann sum, i.e. the sum of the (signed) areas of the rectangles.
2400      * @name Value
2401      * @memberOf Riemannsum.prototype
2402      * @function
2403      * @returns {Number} value of Riemann sum.
2404      */
2405     c.Value = function () {
2406         return this.sum;
2407     };
2408 
2409     /**
2410      * @class
2411      * @ignore
2412      */
2413     c.updateDataArray = function () {
2414         var u = Numerics.riemann(f, n(), type(), this.minX(), this.maxX());
2415         this.dataX = u[0];
2416         this.dataY = u[1];
2417 
2418         // Update "Riemann sum"
2419         this.sum = u[2];
2420     };
2421 
2422     c.addParentsFromJCFunctions([n, type]);
2423 
2424     return c;
2425 };
2426 
2427 JXG.registerElement("riemannsum", JXG.createRiemannsum);
2428 
2429 /**
2430  * @class This element is used to provide a constructor for trace curve (simple locus curve), which is realized as a special curve.
2431  * @pseudo
2432  * @name Tracecurve
2433  * @augments JXG.Curve
2434  * @constructor
2435  * @type Object
2436  * @descript JXG.Curve
2437  * @param {Point} Parent elements of Tracecurve are a
2438  *         glider point and a point whose locus is traced.
2439  * @param {point}
2440  * @see JXG.Curve
2441  * @example
2442  * // Create trace curve.
2443  * var c1 = board.create('circle',[[0, 0], [2, 0]]),
2444  * p1 = board.create('point',[-3, 1]),
2445  * g1 = board.create('glider',[2, 1, c1]),
2446  * s1 = board.create('segment',[g1, p1]),
2447  * p2 = board.create('midpoint',[s1]),
2448  * curve = board.create('tracecurve', [g1, p2]);
2449  *
2450  * </pre><div class="jxgbox" id="JXG5749fb7d-04fc-44d2-973e-45c1951e29ad" style="width: 300px; height: 300px;"></div>
2451  * <script type="text/javascript">
2452  *   var tc1_board = JXG.JSXGraph.initBoard('JXG5749fb7d-04fc-44d2-973e-45c1951e29ad', {boundingbox: [-4, 4, 4, -4], axis: false, showcopyright: false, shownavigation: false});
2453  *   var c1 = tc1_board.create('circle',[[0, 0], [2, 0]]),
2454  *       p1 = tc1_board.create('point',[-3, 1]),
2455  *       g1 = tc1_board.create('glider',[2, 1, c1]),
2456  *       s1 = tc1_board.create('segment',[g1, p1]),
2457  *       p2 = tc1_board.create('midpoint',[s1]),
2458  *       curve = tc1_board.create('tracecurve', [g1, p2]);
2459  * </script><pre>
2460  */
2461 JXG.createTracecurve = function (board, parents, attributes) {
2462     var c, glider, tracepoint, attr;
2463 
2464     if (parents.length !== 2) {
2465         throw new Error(
2466             "JSXGraph: Can't create trace curve with given parent'" +
2467             "\nPossible parent types: [glider, point]"
2468         );
2469     }
2470 
2471     glider = board.select(parents[0]);
2472     tracepoint = board.select(parents[1]);
2473 
2474     if (glider.type !== Const.OBJECT_TYPE_GLIDER || !Type.isPoint(tracepoint)) {
2475         throw new Error(
2476             "JSXGraph: Can't create trace curve with parent types '" +
2477             typeof parents[0] +
2478             "' and '" +
2479             typeof parents[1] +
2480             "'." +
2481             "\nPossible parent types: [glider, point]"
2482         );
2483     }
2484 
2485     attr = Type.copyAttributes(attributes, board.options, "tracecurve");
2486     attr.curvetype = "plot";
2487     c = board.create("curve", [[0], [0]], attr);
2488 
2489     /**
2490      * @class
2491      * @ignore
2492      */
2493     c.updateDataArray = function () {
2494         var i, step, t, el, pEl, x, y, from,
2495             savetrace,
2496             le = this.visProp.numberpoints,
2497             savePos = glider.position,
2498             slideObj = glider.slideObject,
2499             mi = slideObj.minX(),
2500             ma = slideObj.maxX();
2501 
2502         // set step width
2503         step = (ma - mi) / le;
2504         this.dataX = [];
2505         this.dataY = [];
2506 
2507         /*
2508          * For gliders on circles and lines a closed curve is computed.
2509          * For gliders on curves the curve is not closed.
2510          */
2511         if (slideObj.elementClass !== Const.OBJECT_CLASS_CURVE) {
2512             le++;
2513         }
2514 
2515         // Loop over all steps
2516         for (i = 0; i < le; i++) {
2517             t = mi + i * step;
2518             x = slideObj.X(t) / slideObj.Z(t);
2519             y = slideObj.Y(t) / slideObj.Z(t);
2520 
2521             // Position the glider
2522             glider.setPositionDirectly(Const.COORDS_BY_USER, [x, y]);
2523             from = false;
2524 
2525             // Update all elements from the glider up to the trace element
2526             for (el in this.board.objects) {
2527                 if (this.board.objects.hasOwnProperty(el)) {
2528                     pEl = this.board.objects[el];
2529 
2530                     if (pEl === glider) {
2531                         from = true;
2532                     }
2533 
2534                     if (from && pEl.needsRegularUpdate) {
2535                         // Save the trace mode of the element
2536                         savetrace = pEl.visProp.trace;
2537                         pEl.visProp.trace = false;
2538                         pEl.needsUpdate = true;
2539                         pEl.update(true);
2540 
2541                         // Restore the trace mode
2542                         pEl.visProp.trace = savetrace;
2543                         if (pEl === tracepoint) {
2544                             break;
2545                         }
2546                     }
2547                 }
2548             }
2549 
2550             // Store the position of the trace point
2551             this.dataX[i] = tracepoint.X();
2552             this.dataY[i] = tracepoint.Y();
2553         }
2554 
2555         // Restore the original position of the glider
2556         glider.position = savePos;
2557         from = false;
2558 
2559         // Update all elements from the glider to the trace point
2560         for (el in this.board.objects) {
2561             if (this.board.objects.hasOwnProperty(el)) {
2562                 pEl = this.board.objects[el];
2563                 if (pEl === glider) {
2564                     from = true;
2565                 }
2566 
2567                 if (from && pEl.needsRegularUpdate) {
2568                     savetrace = pEl.visProp.trace;
2569                     pEl.visProp.trace = false;
2570                     pEl.needsUpdate = true;
2571                     pEl.update(true);
2572                     pEl.visProp.trace = savetrace;
2573 
2574                     if (pEl === tracepoint) {
2575                         break;
2576                     }
2577                 }
2578             }
2579         }
2580     };
2581 
2582     return c;
2583 };
2584 
2585 JXG.registerElement("tracecurve", JXG.createTracecurve);
2586 
2587 /**
2588      * @class This element is used to provide a constructor for step function, which is realized as a special curve.
2589      *
2590      * In case the data points should be updated after creation time, they can be accessed by curve.xterm and curve.yterm.
2591      * @pseudo
2592      * @name Stepfunction
2593      * @augments JXG.Curve
2594      * @constructor
2595      * @type Curve
2596      * @description JXG.Curve
2597      * @param {Array|Function} Parent1 elements of Stepfunction are two arrays containing the coordinates.
2598      * @param {Array|Function} Parent2
2599      * @see JXG.Curve
2600      * @example
2601      * // Create step function.
2602      var curve = board.create('stepfunction', [[0,1,2,3,4,5], [1,3,0,2,2,1]]);
2603 
2604      * </pre><div class="jxgbox" id="JXG32342ec9-ad17-4339-8a97-ff23dc34f51a" style="width: 300px; height: 300px;"></div>
2605      * <script type="text/javascript">
2606      *   var sf1_board = JXG.JSXGraph.initBoard('JXG32342ec9-ad17-4339-8a97-ff23dc34f51a', {boundingbox: [-1, 5, 6, -2], axis: true, showcopyright: false, shownavigation: false});
2607      *   var curve = sf1_board.create('stepfunction', [[0,1,2,3,4,5], [1,3,0,2,2,1]]);
2608      * </script><pre>
2609      */
2610 JXG.createStepfunction = function (board, parents, attributes) {
2611     var c, attr;
2612     if (parents.length !== 2) {
2613         throw new Error(
2614             "JSXGraph: Can't create step function with given parent'" +
2615             "\nPossible parent types: [array, array|function]"
2616         );
2617     }
2618 
2619     attr = Type.copyAttributes(attributes, board.options, "stepfunction");
2620     c = board.create("curve", parents, attr);
2621     /**
2622      * @class
2623      * @ignore
2624      */
2625     c.updateDataArray = function () {
2626         var i,
2627             j = 0,
2628             len = this.xterm.length;
2629 
2630         this.dataX = [];
2631         this.dataY = [];
2632 
2633         if (len === 0) {
2634             return;
2635         }
2636 
2637         this.dataX[j] = this.xterm[0];
2638         this.dataY[j] = this.yterm[0];
2639         ++j;
2640 
2641         for (i = 1; i < len; ++i) {
2642             this.dataX[j] = this.xterm[i];
2643             this.dataY[j] = this.dataY[j - 1];
2644             ++j;
2645             this.dataX[j] = this.xterm[i];
2646             this.dataY[j] = this.yterm[i];
2647             ++j;
2648         }
2649     };
2650 
2651     return c;
2652 };
2653 
2654 JXG.registerElement("stepfunction", JXG.createStepfunction);
2655 
2656 /**
2657  * @class This element is used to provide a constructor for the graph showing
2658  * the (numerical) derivative of a given curve.
2659  *
2660  * @pseudo
2661  * @name Derivative
2662  * @augments JXG.Curve
2663  * @constructor
2664  * @type JXG.Curve
2665  * @param {JXG.Curve} Parent Curve for which the derivative is generated.
2666  * @see JXG.Curve
2667  * @example
2668  * var cu = board.create('cardinalspline', [[[-3,0], [-1,2], [0,1], [2,0], [3,1]], 0.5, 'centripetal'], {createPoints: false});
2669  * var d = board.create('derivative', [cu], {dash: 2});
2670  *
2671  * </pre><div id="JXGb9600738-1656-11e8-8184-901b0e1b8723" class="jxgbox" style="width: 300px; height: 300px;"></div>
2672  * <script type="text/javascript">
2673  *     (function() {
2674  *         var board = JXG.JSXGraph.initBoard('JXGb9600738-1656-11e8-8184-901b0e1b8723',
2675  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
2676  *     var cu = board.create('cardinalspline', [[[-3,0], [-1,2], [0,1], [2,0], [3,1]], 0.5, 'centripetal'], {createPoints: false});
2677  *     var d = board.create('derivative', [cu], {dash: 2});
2678  *
2679  *     })();
2680  *
2681  * </script><pre>
2682  *
2683  */
2684 JXG.createDerivative = function (board, parents, attributes) {
2685     var c, curve, dx, dy, attr;
2686 
2687     if (parents.length !== 1 && parents[0].class !== Const.OBJECT_CLASS_CURVE) {
2688         throw new Error(
2689             "JSXGraph: Can't create derivative curve with given parent'" +
2690             "\nPossible parent types: [curve]"
2691         );
2692     }
2693 
2694     attr = Type.copyAttributes(attributes, board.options, "curve");
2695 
2696     curve = parents[0];
2697     dx = Numerics.D(curve.X);
2698     dy = Numerics.D(curve.Y);
2699 
2700     c = board.create(
2701         "curve",
2702         [
2703             function (t) {
2704                 return curve.X(t);
2705             },
2706             function (t) {
2707                 return dy(t) / dx(t);
2708             },
2709             curve.minX(),
2710             curve.maxX()
2711         ],
2712         attr
2713     );
2714 
2715     c.setParents(curve);
2716 
2717     return c;
2718 };
2719 
2720 JXG.registerElement("derivative", JXG.createDerivative);
2721 
2722 /**
2723  * @class Intersection of two closed path elements. The elements may be of type curve, circle, polygon, inequality.
2724  * If one element is a curve, it has to be closed.
2725  * The resulting element is of type curve.
2726  * @pseudo
2727  * @name CurveIntersection
2728  * @param {JXG.Curve|JXG.Polygon|JXG.Circle} curve1 First element which is intersected
2729  * @param {JXG.Curve|JXG.Polygon|JXG.Circle} curve2 Second element which is intersected
2730  * @augments JXG.Curve
2731  * @constructor
2732  * @type JXG.Curve
2733  *
2734  * @example
2735  * var f = board.create('functiongraph', ['cos(x)']);
2736  * var ineq = board.create('inequality', [f], {inverse: true, fillOpacity: 0.1});
2737  * var circ = board.create('circle', [[0,0], 4]);
2738  * var clip = board.create('curveintersection', [ineq, circ], {fillColor: 'yellow', fillOpacity: 0.6});
2739  *
2740  * </pre><div id="JXGe2948257-8835-4276-9164-8acccb48e8d4" class="jxgbox" style="width: 300px; height: 300px;"></div>
2741  * <script type="text/javascript">
2742  *     (function() {
2743  *         var board = JXG.JSXGraph.initBoard('JXGe2948257-8835-4276-9164-8acccb48e8d4',
2744  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
2745  *     var f = board.create('functiongraph', ['cos(x)']);
2746  *     var ineq = board.create('inequality', [f], {inverse: true, fillOpacity: 0.1});
2747  *     var circ = board.create('circle', [[0,0], 4]);
2748  *     var clip = board.create('curveintersection', [ineq, circ], {fillColor: 'yellow', fillOpacity: 0.6});
2749  *
2750  *     })();
2751  *
2752  * </script><pre>
2753  *
2754  */
2755 JXG.createCurveIntersection = function (board, parents, attributes) {
2756     var c;
2757 
2758     if (parents.length !== 2) {
2759         throw new Error(
2760             "JSXGraph: Can't create curve intersection with given parent'" +
2761             "\nPossible parent types: [array, array|function]"
2762         );
2763     }
2764 
2765     c = board.create("curve", [[], []], attributes);
2766     /**
2767      * @class
2768      * @ignore
2769      */
2770     c.updateDataArray = function () {
2771         var a = Clip.intersection(parents[0], parents[1], this.board);
2772         this.dataX = a[0];
2773         this.dataY = a[1];
2774     };
2775     return c;
2776 };
2777 
2778 /**
2779  * @class Union of two closed path elements. The elements may be of type curve, circle, polygon, inequality.
2780  * If one element is a curve, it has to be closed.
2781  * The resulting element is of type curve.
2782  * @pseudo
2783  * @name CurveUnion
2784  * @param {JXG.Curve|JXG.Polygon|JXG.Circle} curve1 First element defining the union
2785  * @param {JXG.Curve|JXG.Polygon|JXG.Circle} curve2 Second element defining the union
2786  * @augments JXG.Curve
2787  * @constructor
2788  * @type JXG.Curve
2789  *
2790  * @example
2791  * var f = board.create('functiongraph', ['cos(x)']);
2792  * var ineq = board.create('inequality', [f], {inverse: true, fillOpacity: 0.1});
2793  * var circ = board.create('circle', [[0,0], 4]);
2794  * var clip = board.create('curveunion', [ineq, circ], {fillColor: 'yellow', fillOpacity: 0.6});
2795  *
2796  * </pre><div id="JXGe2948257-8835-4276-9164-8acccb48e8d4" class="jxgbox" style="width: 300px; height: 300px;"></div>
2797  * <script type="text/javascript">
2798  *     (function() {
2799  *         var board = JXG.JSXGraph.initBoard('JXGe2948257-8835-4276-9164-8acccb48e8d4',
2800  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
2801  *     var f = board.create('functiongraph', ['cos(x)']);
2802  *     var ineq = board.create('inequality', [f], {inverse: true, fillOpacity: 0.1});
2803  *     var circ = board.create('circle', [[0,0], 4]);
2804  *     var clip = board.create('curveunion', [ineq, circ], {fillColor: 'yellow', fillOpacity: 0.6});
2805  *
2806  *     })();
2807  *
2808  * </script><pre>
2809  *
2810  */
2811 JXG.createCurveUnion = function (board, parents, attributes) {
2812     var c;
2813 
2814     if (parents.length !== 2) {
2815         throw new Error(
2816             "JSXGraph: Can't create curve union with given parent'" +
2817             "\nPossible parent types: [array, array|function]"
2818         );
2819     }
2820 
2821     c = board.create("curve", [[], []], attributes);
2822     /**
2823      * @class
2824      * @ignore
2825      */
2826     c.updateDataArray = function () {
2827         var a = Clip.union(parents[0], parents[1], this.board);
2828         this.dataX = a[0];
2829         this.dataY = a[1];
2830     };
2831     return c;
2832 };
2833 
2834 /**
2835  * @class Difference of two closed path elements. The elements may be of type curve, circle, polygon, inequality.
2836  * If one element is a curve, it has to be closed.
2837  * The resulting element is of type curve.
2838  * @pseudo
2839  * @name CurveDifference
2840  * @param {JXG.Curve|JXG.Polygon|JXG.Circle} curve1 First element from which the second element is "subtracted"
2841  * @param {JXG.Curve|JXG.Polygon|JXG.Circle} curve2 Second element which is subtracted from the first element
2842  * @augments JXG.Curve
2843  * @constructor
2844  * @type JXG.Curve
2845  *
2846  * @example
2847  * var f = board.create('functiongraph', ['cos(x)']);
2848  * var ineq = board.create('inequality', [f], {inverse: true, fillOpacity: 0.1});
2849  * var circ = board.create('circle', [[0,0], 4]);
2850  * var clip = board.create('curvedifference', [ineq, circ], {fillColor: 'yellow', fillOpacity: 0.6});
2851  *
2852  * </pre><div id="JXGe2948257-8835-4276-9164-8acccb48e8d4" class="jxgbox" style="width: 300px; height: 300px;"></div>
2853  * <script type="text/javascript">
2854  *     (function() {
2855  *         var board = JXG.JSXGraph.initBoard('JXGe2948257-8835-4276-9164-8acccb48e8d4',
2856  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
2857  *     var f = board.create('functiongraph', ['cos(x)']);
2858  *     var ineq = board.create('inequality', [f], {inverse: true, fillOpacity: 0.1});
2859  *     var circ = board.create('circle', [[0,0], 4]);
2860  *     var clip = board.create('curvedifference', [ineq, circ], {fillColor: 'yellow', fillOpacity: 0.6});
2861  *
2862  *     })();
2863  *
2864  * </script><pre>
2865  *
2866  */
2867 JXG.createCurveDifference = function (board, parents, attributes) {
2868     var c;
2869 
2870     if (parents.length !== 2) {
2871         throw new Error(
2872             "JSXGraph: Can't create curve difference with given parent'" +
2873             "\nPossible parent types: [array, array|function]"
2874         );
2875     }
2876 
2877     c = board.create("curve", [[], []], attributes);
2878     /**
2879      * @class
2880      * @ignore
2881      */
2882     c.updateDataArray = function () {
2883         var a = Clip.difference(parents[0], parents[1], this.board);
2884         this.dataX = a[0];
2885         this.dataY = a[1];
2886     };
2887     return c;
2888 };
2889 
2890 JXG.registerElement("curvedifference", JXG.createCurveDifference);
2891 JXG.registerElement("curveintersection", JXG.createCurveIntersection);
2892 JXG.registerElement("curveunion", JXG.createCurveUnion);
2893 
2894 // /**
2895 //  * @class Concat of two path elements, in general neither is a closed path. The parent elements have to be curves, too.
2896 //  * The resulting element is of type curve. The curve points are simply concatenated.
2897 //  * @pseudo
2898 //  * @name CurveConcat
2899 //  * @param {JXG.Curve} curve1 First curve element.
2900 //  * @param {JXG.Curve} curve2 Second curve element.
2901 //  * @augments JXG.Curve
2902 //  * @constructor
2903 //  * @type JXG.Curve
2904 //  */
2905 // JXG.createCurveConcat = function (board, parents, attributes) {
2906 //     var c;
2907 
2908 //     if (parents.length !== 2) {
2909 //         throw new Error(
2910 //             "JSXGraph: Can't create curve difference with given parent'" +
2911 //                 "\nPossible parent types: [array, array|function]"
2912 //         );
2913 //     }
2914 
2915 //     c = board.create("curve", [[], []], attributes);
2916 //     /**
2917 //      * @class
2918 //      * @ignore
2919 //      */
2920 //     c.updateCurve = function () {
2921 //         this.points = parents[0].points.concat(
2922 //                 [new JXG.Coords(Const.COORDS_BY_USER, [NaN, NaN], this.board)]
2923 //             ).concat(parents[1].points);
2924 //         this.numberPoints = this.points.length;
2925 //         return this;
2926 //     };
2927 
2928 //     return c;
2929 // };
2930 
2931 // JXG.registerElement("curveconcat", JXG.createCurveConcat);
2932 
2933 /**
2934  * @class Box plot curve. The direction of the box plot can be either vertical or horizontal which
2935  * is controlled by the attribute "dir".
2936  * @pseudo
2937  * @name Boxplot
2938  * @param {Array} quantiles Array containing at least five quantiles. The elements can be of type number, function or string.
2939  * @param {Number|Function} axis Axis position of the box plot
2940  * @param {Number|Function} width Width of the rectangle part of the box plot. The width of the first and 4th quantile
2941  * is relative to this width and can be controlled by the attribute "smallWidth".
2942  * @augments JXG.Curve
2943  * @constructor
2944  * @type JXG.Curve
2945  *
2946  * @example
2947  * var Q = [ -1, 2, 3, 3.5, 5 ];
2948  *
2949  * var b = board.create('boxplot', [Q, 2, 4], {strokeWidth: 3});
2950  *
2951  * </pre><div id="JXG13eb23a1-a641-41a2-be11-8e03e400a947" class="jxgbox" style="width: 300px; height: 300px;"></div>
2952  * <script type="text/javascript">
2953  *     (function() {
2954  *         var board = JXG.JSXGraph.initBoard('JXG13eb23a1-a641-41a2-be11-8e03e400a947',
2955  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
2956  *     var Q = [ -1, 2, 3, 3.5, 5 ];
2957  *     var b = board.create('boxplot', [Q, 2, 4], {strokeWidth: 3});
2958  *
2959  *     })();
2960  *
2961  * </script><pre>
2962  *
2963  * @example
2964  * var Q = [ -1, 2, 3, 3.5, 5 ];
2965  * var b = board.create('boxplot', [Q, 3, 4], {dir: 'horizontal', smallWidth: 0.25, color:'red'});
2966  *
2967  * </pre><div id="JXG0deb9cb2-84bc-470d-a6db-8be9a5694813" class="jxgbox" style="width: 300px; height: 300px;"></div>
2968  * <script type="text/javascript">
2969  *     (function() {
2970  *         var board = JXG.JSXGraph.initBoard('JXG0deb9cb2-84bc-470d-a6db-8be9a5694813',
2971  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
2972  *     var Q = [ -1, 2, 3, 3.5, 5 ];
2973  *     var b = board.create('boxplot', [Q, 3, 4], {dir: 'horizontal', smallWidth: 0.25, color:'red'});
2974  *
2975  *     })();
2976  *
2977  * </script><pre>
2978  *
2979  * @example
2980  * var data = [57, 57, 57, 58, 63, 66, 66, 67, 67, 68, 69, 70, 70, 70, 70, 72, 73, 75, 75, 76, 76, 78, 79, 81];
2981  * var Q = [];
2982  *
2983  * Q[0] = JXG.Math.Statistics.min(data);
2984  * Q = Q.concat(JXG.Math.Statistics.percentile(data, [25, 50, 75]));
2985  * Q[4] = JXG.Math.Statistics.max(data);
2986  *
2987  * var b = board.create('boxplot', [Q, 0, 3]);
2988  *
2989  * </pre><div id="JXGef079e76-ae99-41e4-af29-1d07d83bf85a" class="jxgbox" style="width: 300px; height: 300px;"></div>
2990  * <script type="text/javascript">
2991  *     (function() {
2992  *         var board = JXG.JSXGraph.initBoard('JXGef079e76-ae99-41e4-af29-1d07d83bf85a',
2993  *             {boundingbox: [-5,90,5,30], axis: true, showcopyright: false, shownavigation: false});
2994  *     var data = [57, 57, 57, 58, 63, 66, 66, 67, 67, 68, 69, 70, 70, 70, 70, 72, 73, 75, 75, 76, 76, 78, 79, 81];
2995  *     var Q = [];
2996  *
2997  *     Q[0] = JXG.Math.Statistics.min(data);
2998  *     Q = Q.concat(JXG.Math.Statistics.percentile(data, [25, 50, 75]));
2999  *     Q[4] = JXG.Math.Statistics.max(data);
3000  *
3001  *     var b = board.create('boxplot', [Q, 0, 3]);
3002  *
3003  *     })();
3004  *
3005  * </script><pre>
3006  *
3007  * @example
3008  * var mi = board.create('glider', [0, -1, board.defaultAxes.y]);
3009  * var ma = board.create('glider', [0, 5, board.defaultAxes.y]);
3010  * var Q = [function() { return mi.Y(); }, 2, 3, 3.5, function() { return ma.Y(); }];
3011  *
3012  * var b = board.create('boxplot', [Q, 0, 2]);
3013  *
3014  * </pre><div id="JXG3b3225da-52f0-42fe-8396-be9016bf289b" class="jxgbox" style="width: 300px; height: 300px;"></div>
3015  * <script type="text/javascript">
3016  *     (function() {
3017  *         var board = JXG.JSXGraph.initBoard('JXG3b3225da-52f0-42fe-8396-be9016bf289b',
3018  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
3019  *     var mi = board.create('glider', [0, -1, board.defaultAxes.y]);
3020  *     var ma = board.create('glider', [0, 5, board.defaultAxes.y]);
3021  *     var Q = [function() { return mi.Y(); }, 2, 3, 3.5, function() { return ma.Y(); }];
3022  *
3023  *     var b = board.create('boxplot', [Q, 0, 2]);
3024  *
3025  *     })();
3026  *
3027  * </script><pre>
3028  *
3029  */
3030 JXG.createBoxPlot = function (board, parents, attributes) {
3031     var box, i, len,
3032         attr = Type.copyAttributes(attributes, board.options, "boxplot");
3033 
3034     if (parents.length !== 3) {
3035         throw new Error(
3036             "JSXGraph: Can't create box plot with given parent'" +
3037             "\nPossible parent types: [array, number|function, number|function] containing quantiles, axis, width"
3038         );
3039     }
3040     if (parents[0].length < 5) {
3041         throw new Error(
3042             "JSXGraph: Can't create box plot with given parent[0]'" +
3043             "\nparent[0] has to contain at least 5 quantiles."
3044         );
3045     }
3046     box = board.create("curve", [[], []], attr);
3047 
3048     len = parents[0].length; // Quantiles
3049     box.Q = [];
3050     for (i = 0; i < len; i++) {
3051         box.Q[i] = Type.createFunction(parents[0][i], board);
3052     }
3053     box.x = Type.createFunction(parents[1], board);
3054     box.w = Type.createFunction(parents[2], board);
3055 
3056     /**
3057      * @class
3058      * @ignore
3059      */
3060     box.updateDataArray = function () {
3061         var v1, v2, l1, l2, r1, r2, w2, dir, x;
3062 
3063         w2 = this.evalVisProp('smallwidth');
3064         dir = this.evalVisProp('dir');
3065         x = this.x();
3066         l1 = x - this.w() * 0.5;
3067         l2 = x - this.w() * 0.5 * w2;
3068         r1 = x + this.w() * 0.5;
3069         r2 = x + this.w() * 0.5 * w2;
3070         v1 = [x, l2, r2, x, x, l1, l1, r1, r1, x, NaN, l1, r1, NaN, x, x, l2, r2, x];
3071         v2 = [
3072             this.Q[0](),
3073             this.Q[0](),
3074             this.Q[0](),
3075             this.Q[0](),
3076             this.Q[1](),
3077             this.Q[1](),
3078             this.Q[3](),
3079             this.Q[3](),
3080             this.Q[1](),
3081             this.Q[1](),
3082             NaN,
3083             this.Q[2](),
3084             this.Q[2](),
3085             NaN,
3086             this.Q[3](),
3087             this.Q[4](),
3088             this.Q[4](),
3089             this.Q[4](),
3090             this.Q[4]()
3091         ];
3092         if (dir === "vertical") {
3093             this.dataX = v1;
3094             this.dataY = v2;
3095         } else {
3096             this.dataX = v2;
3097             this.dataY = v1;
3098         }
3099     };
3100 
3101     box.addParentsFromJCFunctions([box.Q, box.x, box.w]);
3102 
3103     return box;
3104 };
3105 
3106 JXG.registerElement("boxplot", JXG.createBoxPlot);
3107 
3108 /**
3109  *
3110  * @class
3111  * From <a href="https://en.wikipedia.org/wiki/Implicit_curve">Wikipedia</a>:
3112  * "An implicit curve is a plane curve defined by an implicit equation
3113  * relating two coordinate variables, commonly <i>x</i> and <i>y</i>.
3114  * For example, the unit circle is defined by the implicit equation
3115  * x<sup>2</sup> + y<sup>2</sup> = 1.
3116  * In general, every implicit curve is defined by an equation of the form
3117  * <i>f(x, y) = 0</i>
3118  * for some function <i>f</i> of two variables."
3119  * <p>
3120  * The partial derivatives for <i>f</i> are optional. If not given, numerical
3121  * derivatives are used instead. This is good enough for most practical use cases.
3122  * But if supplied, both partial derivatives must be supplied.
3123  * <p>
3124  * The most effective attributes to tinker with if the implicit curve algorithm fails are
3125  * {@link ImplicitCurve#resolution_outer},
3126  * {@link ImplicitCurve#resolution_inner},
3127  * {@link ImplicitCurve#alpha_0},
3128  * {@link ImplicitCurve#h_initial},
3129  * {@link ImplicitCurve#h_max}, and
3130  * {@link ImplicitCurve#qdt_box}.
3131  *
3132  * @pseudo
3133  * @name ImplicitCurve
3134  * @param {Function|String} f Function of two variables for the left side of the equation <i>f(x,y)=0</i>.
3135  * If f is supplied as string, it has to use the variables 'x' and 'y'.
3136  * @param {Function|String} [dfx=null] Optional partial derivative in respect to the first variable
3137  * If dfx is supplied as string, it has to use the variables 'x' and 'y'.
3138  * @param {Function|String} [dfy=null] Optional partial derivative in respect to the second variable
3139  * If dfy is supplied as string, it has to use the variables 'x' and 'y'.
3140  * @param {Array|Function} [rangex=boundingbox] Optional array of length 2
3141  * of the form [x_min, x_max] setting the domain of the x coordinate of the implicit curve.
3142  * If not supplied, the board's boundingbox (+ the attribute "margin") is taken.
3143  * For algorithmic reasons, the plotted curve mighty slightly overflow the given domain.
3144  * @param {Array|Function} [rangey=boundingbox] Optional array of length 2
3145  * of the form [y_min, y_max] setting the domain of the y coordinate of the implicit curve.
3146  * If not supplied, the board's boundingbox (+ the attribute "margin") is taken.
3147  * For algorithmic reasons, the plotted curve mighty slightly overflow the given domain.
3148  * @augments JXG.Curve
3149  * @constructor
3150  * @type JXG.Curve
3151  *
3152  * @example
3153  *   var f, c;
3154  *   f = (x, y) => 1 / 16 * x ** 2 + y ** 2 - 1;
3155  *   c = board.create('implicitcurve', [f], {
3156  *       strokeWidth: 3,
3157  *       strokeColor: JXG.palette.red,
3158  *       strokeOpacity: 0.8
3159  *   });
3160  *
3161  * </pre><div id="JXGa6e86701-1a82-48d0-b007-3a3d32075076" class="jxgbox" style="width: 300px; height: 300px;"></div>
3162  * <script type="text/javascript">
3163  *     (function() {
3164  *         var board = JXG.JSXGraph.initBoard('JXGa6e86701-1a82-48d0-b007-3a3d32075076',
3165  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
3166  *             var f, c;
3167  *             f = (x, y) => 1 / 16 * x ** 2 + y ** 2 - 1;
3168  *             c = board.create('implicitcurve', [f], {
3169  *                 strokeWidth: 3,
3170  *                 strokeColor: JXG.palette.red,
3171  *                 strokeOpacity: 0.8
3172  *             });
3173  *
3174  *     })();
3175  *
3176  * </script><pre>
3177  *
3178  * @example
3179  *  var a, c, f;
3180  *  a = board.create('slider', [[-3, 6], [3, 6], [-3, 1, 3]], {
3181  *      name: 'a', stepWidth: 0.1
3182  *  });
3183  *  f = (x, y) => x ** 2 - 2 * x * y - 2 * x + (a.Value() + 1) * y ** 2 + (4 * a.Value() + 2) * y + 4 * a.Value() - 3;
3184  *  c = board.create('implicitcurve', [f], {
3185  *      strokeWidth: 3,
3186  *      strokeColor: JXG.palette.red,
3187  *      strokeOpacity: 0.8,
3188  *      resolution_outer: 20,
3189  *      resolution_inner: 20
3190  *  });
3191  *
3192  * </pre><div id="JXG0b133a54-9509-4a65-9722-9c5145e23b40" class="jxgbox" style="width: 300px; height: 300px;"></div>
3193  * <script type="text/javascript">
3194  *     (function() {
3195  *         var board = JXG.JSXGraph.initBoard('JXG0b133a54-9509-4a65-9722-9c5145e23b40',
3196  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
3197  *             var a, c, f;
3198  *             a = board.create('slider', [[-3, 6], [3, 6], [-3, 1, 3]], {
3199  *                 name: 'a', stepWidth: 0.1
3200  *             });
3201  *             f = (x, y) => x ** 2 - 2 * x * y - 2 * x + (a.Value() + 1) * y ** 2 + (4 * a.Value() + 2) * y + 4 * a.Value() - 3;
3202  *             c = board.create('implicitcurve', [f], {
3203  *                 strokeWidth: 3,
3204  *                 strokeColor: JXG.palette.red,
3205  *                 strokeOpacity: 0.8,
3206  *                 resolution_outer: 20,
3207  *                 resolution_inner: 20
3208  *             });
3209  *
3210  *     })();
3211  *
3212  * </script><pre>
3213  *
3214  * @example
3215  *  var c = board.create('implicitcurve', ['abs(x * y) - 3'], {
3216  *      strokeWidth: 3,
3217  *      strokeColor: JXG.palette.red,
3218  *      strokeOpacity: 0.8
3219  *  });
3220  *
3221  * </pre><div id="JXG02802981-0abb-446b-86ea-ee588f02ed1a" class="jxgbox" style="width: 300px; height: 300px;"></div>
3222  * <script type="text/javascript">
3223  *     (function() {
3224  *         var board = JXG.JSXGraph.initBoard('JXG02802981-0abb-446b-86ea-ee588f02ed1a',
3225  *             {boundingbox: [-8, 8, 8,-8], axis: true, showcopyright: false, shownavigation: false});
3226  *             var c = board.create('implicitcurve', ['abs(x * y) - 3'], {
3227  *                 strokeWidth: 3,
3228  *                 strokeColor: JXG.palette.red,
3229  *                 strokeOpacity: 0.8
3230  *             });
3231  *
3232  *     })();
3233  *
3234  * </script><pre>
3235  *
3236  * @example
3237  * var niveauline = [];
3238  * niveauline = [0.5, 1, 1.5, 2];
3239  * for (let i = 0; i < niveauline.length; i++) {
3240  *     board.create("implicitcurve", [
3241  *         (x, y) => x ** .5 * y ** .5 - niveauline[i],
3242            [0.25, 3], [0.5, 4] // Domain
3243  *     ], {
3244  *         strokeWidth: 2,
3245  *         strokeColor: JXG.palette.red,
3246  *         strokeOpacity: (1 + i) / niveauline.length,
3247  *         needsRegularUpdate: false
3248  *     });
3249  * }
3250  *
3251  * </pre><div id="JXGccee9aab-6dd9-4a79-827d-3164f70cc6a1" class="jxgbox" style="width: 300px; height: 300px;"></div>
3252  * <script type="text/javascript">
3253  *     (function() {
3254  *         var board = JXG.JSXGraph.initBoard('JXGccee9aab-6dd9-4a79-827d-3164f70cc6a1',
3255  *             {boundingbox: [-1, 5, 5,-1], axis: true, showcopyright: false, shownavigation: false});
3256  *         var niveauline = [];
3257  *         niveauline = [0.5, 1, 1.5, 2];
3258  *         for (let i = 0; i < niveauline.length; i++) {
3259  *             board.create("implicitcurve", [
3260  *                 (x, y) => x ** .5 * y ** .5 - niveauline[i],
3261  *                 [0.25, 3], [0.5, 4]
3262  *             ], {
3263  *                 strokeWidth: 2,
3264  *                 strokeColor: JXG.palette.red,
3265  *                 strokeOpacity: (1 + i) / niveauline.length,
3266  *                 needsRegularUpdate: false
3267  *             });
3268  *         }
3269  *
3270  *     })();
3271  *
3272  * </script><pre>
3273  *
3274  */
3275 JXG.createImplicitCurve = function (board, parents, attributes) {
3276     var c, attr;
3277 
3278     if ([1, 3, 5].indexOf(parents.length) < 0) {
3279         throw new Error(
3280             "JSXGraph: Can't create curve implicitCurve with given parent'" +
3281             "\nPossible parent types: [f], [f, rangex, rangey], [f, dfx, dfy] or [f, dfx, dfy, rangex, rangey]" +
3282             "\nwith functions f, dfx, dfy and arrays of length 2 rangex, rangey."
3283         );
3284     }
3285 
3286     // if (parents.length === 3) {
3287     //     if (!Type.isArray(parents[1]) && !Type.isArray(parents[2])) {
3288     //         throw new Error(
3289     //             "JSXGraph: Can't create curve implicitCurve with given parent'" +
3290     //             "\nPossible parent types: [f], [f, rangex, rangey], [f, dfx, dfy] or [f, dfx, dfy, rangex, rangey]" +
3291     //             "\nwith functions f, dfx, dfy and arrays of length 2 rangex, rangey."
3292     //         );
3293     //     }
3294     // }
3295     // if (parents.length === 5) {
3296     //     if (!Type.isArray(parents[3]) && !Type.isArray(parents[4])) {
3297     //         throw new Error(
3298     //             "JSXGraph: Can't create curve implicitCurve with given parent'" +
3299     //             "\nPossible parent types: [f], [f, rangex, rangey], [f, dfx, dfy] or [f, dfx, dfy, rangex, rangey]" +
3300     //             "\nwith functions f, dfx, dfy and arrays of length 2 rangex, rangey."
3301     //         );
3302     //     }
3303     // }
3304 
3305     attr = Type.copyAttributes(attributes, board.options, "implicitcurve");
3306     c = board.create("curve", [[], []], attr);
3307 
3308     /**
3309      * Function of two variables for the left side of the equation <i>f(x,y)=0</i>.
3310      *
3311      * @name f
3312      * @memberOf ImplicitCurve.prototype
3313      * @function
3314      * @returns {Number}
3315      */
3316     c.f = Type.createFunction(parents[0], board, 'x, y');
3317 
3318     /**
3319      * Partial derivative in the first variable of
3320      * the left side of the equation <i>f(x,y)=0</i>.
3321      * If null, then numerical derivative is used.
3322      *
3323      * @name dfx
3324      * @memberOf ImplicitCurve.prototype
3325      * @function
3326      * @returns {Number}
3327      */
3328     c.dfx = Type.createFunction(parents[1], board, 'x, y');
3329 
3330     /**
3331      * Partial derivative in the second variable of
3332      * the left side of the equation <i>f(x,y)=0</i>.
3333      * If null, then numerical derivative is used.
3334      *
3335      * @name dfy
3336      * @memberOf ImplicitCurve.prototype
3337      * @function
3338      * @returns {Number}
3339      */
3340     c.dfy = Type.createFunction(parents[2], board, 'x, y');
3341 
3342     /**
3343      * Defines a domain for searching f(x,y)=0. Default is null, meaning
3344      * the bounding box of the board is used.
3345      * Using domain, visProp.margin is ignored.
3346      * @name domain
3347      * @memberOf ImplicitCurve.prototype
3348      * @param {Array} of length 4 defining the domain used to compute the implict curve.
3349      * Syntax: [x_min, y_max, x_max, y_min]
3350      */
3351     // c.domain = board.getBoundingBox();
3352     c.domain = null;
3353     if (parents.length === 5) {
3354         c.domain = [parents[3], parents[4]];
3355         // c.visProp.margin = 0;
3356     } else if (parents.length === 3) {
3357         c.domain = [parents[1], parents[2]];
3358         // c.visProp.margin = 0;
3359     }
3360 
3361     /**
3362      * @class
3363      * @ignore
3364      */
3365     c.updateDataArray = function () {
3366         var bbox, rx, ry,
3367             ip, cfg,
3368             ret = [],
3369             mgn;
3370 
3371         if (this.domain === null) {
3372             mgn = this.evalVisProp('margin');
3373             bbox = this.board.getBoundingBox();
3374             bbox[0] -= mgn;
3375             bbox[1] += mgn;
3376             bbox[2] += mgn;
3377             bbox[3] -= mgn;
3378         } else {
3379             rx = Type.evaluate(this.domain[0]);
3380             ry = Type.evaluate(this.domain[1]);
3381             bbox = [rx[0], ry[1], rx[1], ry[0]];
3382         }
3383 
3384         cfg = {
3385             resolution_out: Math.max(0.01, this.evalVisProp('resolution_outer')),
3386             resolution_in: Math.max(0.01, this.evalVisProp('resolution_inner')),
3387             max_steps: this.evalVisProp('max_steps'),
3388             alpha_0: this.evalVisProp('alpha_0'),
3389             tol_u0: this.evalVisProp('tol_u0'),
3390             tol_newton: this.evalVisProp('tol_newton'),
3391             tol_cusp: this.evalVisProp('tol_cusp'),
3392             tol_progress: this.evalVisProp('tol_progress'),
3393             qdt_box: this.evalVisProp('qdt_box'),
3394             kappa_0: this.evalVisProp('kappa_0'),
3395             delta_0: this.evalVisProp('delta_0'),
3396             h_initial: this.evalVisProp('h_initial'),
3397             h_critical: this.evalVisProp('h_critical'),
3398             h_max: this.evalVisProp('h_max'),
3399             loop_dist: this.evalVisProp('loop_dist'),
3400             loop_dir: this.evalVisProp('loop_dir'),
3401             loop_detection: this.evalVisProp('loop_detection'),
3402             unitX: this.board.unitX,
3403             unitY: this.board.unitY
3404         };
3405         this.dataX = [];
3406         this.dataY = [];
3407 
3408         // console.time("implicit plot");
3409         ip = new ImplicitPlot(bbox, cfg, this.f, this.dfx, this.dfy);
3410         this.qdt = ip.qdt;
3411 
3412         ret = ip.plot();
3413         // console.timeEnd("implicit plot");
3414 
3415         this.dataX = ret[0];
3416         this.dataY = ret[1];
3417     };
3418 
3419     c.elType = 'implicitcurve';
3420 
3421     return c;
3422 };
3423 
3424 JXG.registerElement("implicitcurve", JXG.createImplicitCurve);
3425 
3426 
3427 export default JXG.Curve;
3428 
3429 // export default {
3430 //     Curve: JXG.Curve,
3431 //     createCardinalSpline: JXG.createCardinalSpline,
3432 //     createCurve: JXG.createCurve,
3433 //     createCurveDifference: JXG.createCurveDifference,
3434 //     createCurveIntersection: JXG.createCurveIntersection,
3435 //     createCurveUnion: JXG.createCurveUnion,
3436 //     createDerivative: JXG.createDerivative,
3437 //     createFunctiongraph: JXG.createFunctiongraph,
3438 //     createMetapostSpline: JXG.createMetapostSpline,
3439 //     createPlot: JXG.createFunctiongraph,
3440 //     createSpline: JXG.createSpline,
3441 //     createRiemannsum: JXG.createRiemannsum,
3442 //     createStepfunction: JXG.createStepfunction,
3443 //     createTracecurve: JXG.createTracecurve
3444 // };
3445 
3446 // const Curve = JXG.Curve;
3447 // export { Curve as default, Curve};
3448