geogebra.kernel.implicit.GeoImplicitPoly.java Source code

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/* 
GeoGebra - Dynamic Mathematics for Everyone
http://www.geogebra.org
    
This file is part of GeoGebra.
    
This program is free software; you can redistribute it and/or modify it 
under the terms of the GNU General Public License as published by 
the Free Software Foundation.
    
*/

/*
 * GeoImplicitPoly.java
 *
 * Created on 03. June 2010, 11:57
 */

package geogebra.kernel.implicit;

import geogebra.euclidian.EuclidianViewInterface;
import geogebra.kernel.AlgoClosestPoint;
import geogebra.kernel.AlgoElement;
import geogebra.kernel.AlgoPointOnPath;
import geogebra.kernel.ConicMirrorable;
import geogebra.kernel.Construction;
import geogebra.kernel.Dilateable;
import geogebra.kernel.EuclidianViewCE;
import geogebra.kernel.GeoConic;
import geogebra.kernel.GeoElement;
import geogebra.kernel.GeoLine;
import geogebra.kernel.GeoList;
import geogebra.kernel.GeoLocus;
import geogebra.kernel.GeoPoint;
import geogebra.kernel.GeoUserInputElement;
import geogebra.kernel.Kernel;
import geogebra.kernel.Mirrorable;
import geogebra.kernel.MyPoint;
import geogebra.kernel.Path;
import geogebra.kernel.PathMover;
import geogebra.kernel.PointRotateable;
import geogebra.kernel.Traceable;
import geogebra.kernel.Transformable;
import geogebra.kernel.Translateable;
import geogebra.kernel.Matrix.Coords;
import geogebra.kernel.arithmetic.ExpressionNode;
import geogebra.kernel.arithmetic.ExpressionValue;
import geogebra.kernel.arithmetic.NumberValue;
import geogebra.kernel.arithmetic.Polynomial;
import geogebra.kernel.kernelND.GeoPointND;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

import org.apache.commons.math.linear.DecompositionSolver;
import org.apache.commons.math.linear.LUDecompositionImpl;
import org.apache.commons.math.linear.RealMatrix;
import org.apache.commons.math.linear.RealMatrixImpl;

/**
 * Represents implicit bivariat polynomial equations, with degree greater than 2.
 */
public class GeoImplicitPoly extends GeoUserInputElement implements Path, Traceable, Mirrorable, ConicMirrorable,
        Translateable, PointRotateable, Dilateable, Transformable, EuclidianViewCE {

    private double[][] coeff;
    private double[][] coeffSquarefree;
    private int degX;
    private int degY;

    private boolean defined = true;
    private boolean isConstant;
    private boolean calcPath;

    private boolean trace; //for traceable interface

    public GeoLocus locus;
    public Polynomial poly;

    public GeoImplicitPoly(Construction c) {
        super(c);
        degX = -1;
        degY = -1;
        coeffSquarefree = new double[0][0];
        locus = new GeoLocus(c);
        locus.setDefined(true);
        calcPath = true;
        c.registerEuclidianViewCE(this);
    }

    private GeoImplicitPoly(Construction c, String label, double[][] coeff, boolean calcPath) {
        this(c);
        setLabel(label);
        this.calcPath = calcPath;
        setCoeff(coeff, calcPath);
        if (!calcPath)
            c.unregisterEuclidianViewCE(this);
    }

    protected GeoImplicitPoly(Construction c, String label, double[][] coeff) {
        this(c, label, coeff, true);
    }

    private GeoImplicitPoly(Construction c, String label, Polynomial poly, boolean calcPath) {
        this(c);
        this.poly = poly;
        setLabel(label);
        this.calcPath = calcPath;
        setCoeff(poly.getCoeff(), calcPath);
        if (!calcPath)
            c.unregisterEuclidianViewCE(this);
    }

    public GeoImplicitPoly(Construction c, String label, Polynomial poly) {
        this(c, label, poly, true);
    }

    /**
     * 
     * @param c
     * @param coeff
     * @return a GeoImplicitPoly witch doesn't calculate it's path.
     */
    public static GeoImplicitPoly createImplicitPolyWithoutPath(Construction c, double[][] coeff) {
        return new GeoImplicitPoly(c, null, coeff, false);
    }

    /**
     * The curve will no longer update the Path and won't receive updates
     * when the euclidian View changes.
     * Useful if the curve is used as a container for helper algorithms.
     * This method should be called directly after instantiation, via the one
     * argument constructor, if the coefficients are present already
     * {@link #createImplicitPolyWithoutPath}
     */
    public void preventPathCreation() {
        calcPath = false;
        cons.unregisterEuclidianViewCE(this);
    }

    public GeoImplicitPoly(GeoImplicitPoly g) {
        this(g.cons);
        set(g);
    }

    /* 
     *               ( A[0]  A[3]    A[4] )
     *      matrix = ( A[3]  A[1]    A[5] )
     *               ( A[4]  A[5]    A[2] )
     */

    /**
     * Construct GeoImplicitPoly from GeoConic
     * @param c
     */
    public GeoImplicitPoly(GeoConic c) {
        this(c.getConstruction());
        coeff = new double[3][3];
        coeff[0][0] = c.matrix[2];
        coeff[1][1] = 2 * c.matrix[3];
        coeff[2][2] = 0;
        coeff[1][0] = 2 * c.matrix[4];
        coeff[0][1] = 2 * c.matrix[5];
        coeff[2][0] = c.matrix[0];
        coeff[0][2] = c.matrix[1];
        coeff[2][1] = coeff[1][2] = 0;
        degX = 2;
        degY = 2;
    }

    @Override
    public GeoElement copy() {
        return new GeoImplicitPoly(this);
    }

    @Override
    public int getGeoClassType() {
        return GEO_CLASS_IMPLICIT_POLY;
    }

    @Override
    protected String getTypeString() {
        return "ImplicitPoly";
    }

    /**
     * returns all class-specific xml tags for saveXML
     */
    protected void getXMLtags(StringBuilder sb) {
        super.getXMLtags(sb);
        getLineStyleXML(sb);

        sb.append("\t<coefficients rep=\"array\" data=\"");
        sb.append("[");
        for (int i = 0; i < coeff.length; i++) {
            if (i > 0)
                sb.append(',');
            sb.append("[");
            for (int j = 0; j < coeff[i].length; j++) {
                if (j > 0)
                    sb.append(',');
                sb.append(coeff[i][j]);
            }
            sb.append("]");
        }
        sb.append("]");
        sb.append("\" />\n");
    }

    @Override
    public boolean isDefined() {
        return defined && locus.isDefined() && locus.getMyPointList().size() > 0;
    }

    public boolean getDefined() {
        return defined;
    }

    @Override
    public boolean isEqual(GeoElement Geo) {
        if (Geo instanceof GeoImplicitPoly) {
            GeoImplicitPoly imp = (GeoImplicitPoly) Geo;
            for (int i = 0; i < Math.max(imp.coeff.length, coeff.length); i++) {
                int l = 0;
                if (i < imp.coeff.length)
                    l = imp.coeff[i].length;
                if (i < coeff.length) {
                    l = Math.max(l, coeff[i].length);
                }
                for (int j = 0; j < l; j++) {
                    double c = 0;
                    if (i < imp.coeff.length) {
                        if (j < imp.coeff[i].length) {
                            c = imp.coeff[i][j];
                        }
                    }
                    double d = 0;
                    if (i < coeff.length) {
                        if (j < coeff[i].length) {
                            d = coeff[i][j];
                        }
                    }
                    if (!Kernel.isEqual(c, d))
                        return false;
                }
            }
            return true;
        }
        return false;
    }

    @Override
    public boolean isGeoImplicitPoly() {
        return true;
    }

    @Override
    public boolean isPath() {
        return true;
    }

    @Override
    public void set(GeoElement geo) {
        if (!(geo instanceof GeoImplicitPoly))
            return;
        super.set(geo);
        setCoeff(((GeoImplicitPoly) geo).getCoeff(), false);
        locus.set(((GeoImplicitPoly) geo).locus);
        this.defined = ((GeoImplicitPoly) geo).getDefined();
    }

    @Override
    public void setUndefined() {
        defined = false;
    }

    public void setDefined() {
        defined = true;
    }

    @Override
    public boolean showInAlgebraView() {
        return true;
    }

    @Override
    protected boolean showInEuclidianView() {
        return true;
    }

    private void addPow(StringBuilder sb, int i) {
        if (i > 1) {
            if (kernel.getCASPrintForm() == ExpressionNode.STRING_TYPE_LATEX) {
                sb.append('^');
                sb.append('{');
                sb.append(i);
                sb.append('}');
            } else if ((kernel.getCASPrintForm() == ExpressionNode.STRING_TYPE_JASYMCA)
                    || (kernel.getCASPrintForm() == ExpressionNode.STRING_TYPE_GEOGEBRA_XML)
                    || (kernel.getCASPrintForm() == ExpressionNode.STRING_TYPE_MATH_PIPER)
                    || (kernel.getCASPrintForm() == ExpressionNode.STRING_TYPE_MAXIMA)
                    || (kernel.getCASPrintForm() == ExpressionNode.STRING_TYPE_MPREDUCE)) {
                sb.append('^');
                sb.append(i);
            } else {
                String p = "";
                while (i > 0) {
                    int c = i % 10;
                    switch (c) {
                    case 1:
                        p = '\u00b9' + p;
                        break;
                    case 2:
                        p = '\u00b2' + p;
                        break;
                    case 3:
                        p = '\u00b3' + p;
                        break;
                    default:
                        p = (char) ('\u2070' + c) + p;
                    }
                    i = i / 10;
                }
                sb.append(p);
            }
        }
    }

    @Override
    protected String toRawValueString() {
        if (coeff == null)
            return "";
        StringBuilder sb = new StringBuilder();
        boolean first = true;
        for (int i = coeff.length - 1; i >= 0; i--) {
            for (int j = coeff[i].length - 1; j >= 0; j--) {
                if (i == 0 && j == 0) {
                    if (first)
                        sb.append("0");
                    if (kernel.getCASPrintForm() == ExpressionNode.STRING_TYPE_MATH_PIPER)
                        sb.append("== ");
                    else
                        sb.append("= ");
                    sb.append(kernel.format(-coeff[0][0]));
                } else {
                    String number = kernel.format(coeff[i][j]);
                    boolean pos = true;
                    if (number.charAt(0) == '-') {
                        pos = false;
                        number = number.substring(1);
                    }
                    if (!number.equals("0")) {
                        if (pos) {
                            if (!first) {
                                sb.append('+');
                            }
                        } else {
                            sb.append('-');
                        }
                        if (!first) {
                            sb.append(' ');
                        }
                        first = false;
                        if (!number.equals("1")) {
                            sb.append(number);
                        }
                        if (i > 0) {
                            sb.append('x');
                        }
                        addPow(sb, i);
                        if (j > 0) {
                            if (i > 0) { //insert blank after x^i
                                sb.append(' ');
                            }
                            sb.append('y');
                        }
                        addPow(sb, j);
                        sb.append(' ');
                    }
                }
            }
        }

        return sb.toString();
    }

    @Override
    public String getClassName() {
        return "GeoImplicitPoly";
    }

    public boolean isVector3DValue() {
        return false;
    }

    /**
     * @param c assigns given coefficient-array to be the coefficients of this Polynomial.
     */
    public void setCoeff(double[][] c) {
        setCoeff(c, true);
    }

    /**
     * @param c assigns given coefficient-array to be the coefficients of this Polynomial.
     * @param calcPath : the path should be calculated "new".
     */
    public void setCoeff(double[][] c, boolean calcPath) {
        isConstant = true;
        degX = -1;
        degY = -1;
        coeffSquarefree = null;
        degX = c.length - 1;
        coeff = new double[c.length][];
        for (int i = 0; i < c.length; i++) {
            coeff[i] = new double[c[i].length];
            if (c[i].length > degY + 1)
                degY = c[i].length - 1;
            for (int j = 0; j < c[i].length; j++) {
                coeff[i][j] = c[i][j];
                isConstant = isConstant && (c[i][j] == 0 || (i == 0 && j == 0));
            }
        }
        if (calcPath && this.calcPath)
            updatePath();
    }

    /**
     * @param ev assigns given coefficient-array to be the coefficients of this Polynomial.
     */
    public void setCoeff(ExpressionValue[][] ev) {
        setCoeff(ev, true);
    }

    /**
     * @param ev assigns given coefficient-array to be the coefficients of this Polynomial.
     * @param calcPath 
     */
    public void setCoeff(ExpressionValue[][] ev, boolean calcPath) {
        isConstant = true;
        degX = -1;
        degY = -1;
        coeff = new double[ev.length][];
        degX = ev.length - 1;
        coeffSquarefree = null;
        for (int i = 0; i < ev.length; i++) {
            coeff[i] = new double[ev[i].length];
            if (ev[i].length > degY + 1)
                degY = ev[i].length - 1;
            for (int j = 0; j < ev[i].length; j++) {
                if (ev[i][j] == null)
                    coeff[i][j] = 0;
                else
                    coeff[i][j] = ((NumberValue) ev[i][j].evaluate()).getDouble();
                isConstant = isConstant && (Kernel.isZero(coeff[i][j]) || (i == 0 && j == 0));
            }
        }
        getFactors();
        if (calcPath && this.calcPath)
            updatePath();
    }

    /**
     * @param squarefree if squarefree is true returns a squarefree representation of this polynomial
     * is such representation is available
     * @return coefficient array of this implicit polynomial equation
     */
    public double[][] getCoeff(boolean squarefree) {
        if (squarefree && coeffSquarefree != null) {
            return coeffSquarefree;
        } else
            return coeff;
    }

    /**
     * @return coefficient array of this implicit polynomial equation
     */
    public double[][] getCoeff() {
        return coeff;
    }

    public double evalPolyAt(double x, double y) {
        return evalPolyAt(x, y, false);
    }

    public double evalPolyAt(double x, double y, boolean squarefree) {
        return evalPolyCoeffAt(x, y, getCoeff(squarefree));
    }

    public double evalPolyCoeffAt(double x, double y, double[][] coeff) {
        double sum = 0;
        double zs = 0;
        //Evaluating Poly via the Horner-scheme
        if (coeff != null)
            for (int i = coeff.length - 1; i >= 0; i--) {
                zs = 0;
                for (int j = coeff[i].length - 1; j >= 0; j--) {
                    zs = y * zs + coeff[i][j];
                }
                sum = sum * x + zs;
            }
        return sum;
    }

    public double evalDiffXPolyAt(double x, double y) {
        return evalDiffXPolyAt(x, y, false);
    }

    public double evalDiffXPolyAt(double x, double y, boolean squarefree) {
        double sum = 0;
        double zs = 0;
        double[][] coeff = getCoeff(squarefree);
        //Evaluating Poly via the Horner-scheme
        if (coeff != null)
            for (int i = coeff.length - 1; i >= 1; i--) {
                zs = 0;
                for (int j = coeff[i].length - 1; j >= 0; j--) {
                    zs = y * zs + coeff[i][j];
                }
                sum = sum * x + i * zs;
            }
        return sum;
    }

    public double evalDiffYPolyAt(double x, double y) {
        return evalDiffYPolyAt(x, y, false);
    }

    public double evalDiffYPolyAt(double x, double y, boolean squarefree) {
        double sum = 0;
        double zs = 0;
        double[][] coeff = getCoeff(squarefree);
        //Evaluating Poly via the Horner-scheme
        if (coeff != null)
            for (int i = coeff.length - 1; i >= 0; i--) {
                zs = 0;
                for (int j = coeff[i].length - 1; j >= 1; j--) {
                    zs = y * zs + j * coeff[i][j];
                }
                sum = sum * x + zs;
            }
        return sum;
    }

    /**
     * Plugs in two rational polynomials for x and y, x|->pX/qX and y|->pY/qY in the curve 
     * (replacing the current coefficients with the new ones)
     * [not yet tested for qX!=qY]
     * @param pX
     * @param pY
     * @param qX
     * @param qY
     */
    public void plugInRatPoly(double[][] pX, double[][] pY, double[][] qX, double[][] qY) {
        int degXpX = pX.length - 1;
        int degYpX = 0;
        for (int i = 0; i < pX.length; i++) {
            if (pX[i].length - 1 > degYpX)
                degYpX = pX[i].length - 1;
        }
        int degXqX = -1;
        int degYqX = -1;
        if (qX != null) {
            degXqX = qX.length - 1;
            for (int i = 0; i < qX.length; i++) {
                if (qX[i].length - 1 > degYqX)
                    degYqX = qX[i].length - 1;
            }
        }
        int degXpY = pY.length - 1;
        int degYpY = 0;
        for (int i = 0; i < pY.length; i++) {
            if (pY[i].length - 1 > degYpY)
                degYpY = pY[i].length - 1;
        }
        int degXqY = -1;
        int degYqY = -1;
        if (qY != null) {
            degXqY = qY.length - 1;
            for (int i = 0; i < qY.length; i++) {
                if (qY[i].length - 1 > degYqY)
                    degYqY = qY[i].length - 1;
            }
        }
        boolean sameDenom = false;
        if (qX != null && qY != null) {
            sameDenom = true;
            if (degXqX == degXqY && degYqX == degYqY) {
                for (int i = 0; i < qX.length; i++)
                    if (!Arrays.equals(qY[i], qX[i])) {
                        sameDenom = false;
                        break;
                    }
            }
        }
        int commDeg = 0;
        if (sameDenom) {
            //find the "common" degree, e.g. x^4+y^4->4, but x^4 y^4->8
            commDeg = getDeg();
        }
        int newDegX = Math.max(degXpX, degXqX) * degX + Math.max(degXpY, degXqY) * degY;
        int newDegY = Math.max(degYpX, degYqX) * degX + Math.max(degYpY, degYqY) * degY;

        double[][] newCoeff = new double[newDegX + 1][newDegY + 1];
        double[][] tmpCoeff = new double[newDegX + 1][newDegY + 1];
        double[][] ratXCoeff = new double[newDegX + 1][newDegY + 1];
        double[][] ratYCoeff = new double[newDegX + 1][newDegY + 1];
        int tmpCoeffDegX = 0;
        int tmpCoeffDegY = 0;
        int newCoeffDegX = 0;
        int newCoeffDegY = 0;
        int ratXCoeffDegX = 0;
        int ratXCoeffDegY = 0;
        int ratYCoeffDegX = 0;
        int ratYCoeffDegY = 0;

        for (int i = 0; i < newDegX; i++) {
            for (int j = 0; j < newDegY; j++) {
                newCoeff[i][j] = 0;
                tmpCoeff[i][j] = 0;
                ratXCoeff[i][j] = 0;
                ratYCoeff[i][j] = 0;
            }
        }
        ratXCoeff[0][0] = 1;
        for (int x = coeff.length - 1; x >= 0; x--) {
            if (qY != null) {
                ratYCoeff[0][0] = 1;
                ratYCoeffDegX = 0;
                ratYCoeffDegY = 0;
            }
            int startY = coeff[x].length - 1;
            if (sameDenom)
                startY = commDeg - x;
            for (int y = startY; y >= 0; y--) {
                if (qY == null || y == startY) {
                    if (coeff[x].length > y)
                        tmpCoeff[0][0] += coeff[x][y];
                } else {
                    polyMult(ratYCoeff, qY, ratYCoeffDegX, ratYCoeffDegY, degXqY, degYqY); //y^N-i
                    ratYCoeffDegX += degXqY;
                    ratYCoeffDegY += degYqY;
                    if (coeff[x].length > y)
                        for (int i = 0; i <= ratYCoeffDegX; i++) {
                            for (int j = 0; j <= ratYCoeffDegY; j++) {
                                tmpCoeff[i][j] += coeff[x][y] * ratYCoeff[i][j];
                                if (y == 0) {
                                    ratYCoeff[i][j] = 0; //clear in last loop
                                }
                            }
                        }
                    tmpCoeffDegX = Math.max(tmpCoeffDegX, ratYCoeffDegX);
                    tmpCoeffDegY = Math.max(tmpCoeffDegY, ratYCoeffDegY);
                }
                if (y > 0) {
                    polyMult(tmpCoeff, pY, tmpCoeffDegX, tmpCoeffDegY, degXpY, degYpY);
                    tmpCoeffDegX += degXpY;
                    tmpCoeffDegY += degYpY;
                }
            }
            if (qX != null && x != coeff.length - 1 && !sameDenom) {
                polyMult(ratXCoeff, qX, ratXCoeffDegX, ratXCoeffDegY, degXqX, degYqX);
                ratXCoeffDegX += degXqX;
                ratXCoeffDegY += degYqX;
                polyMult(tmpCoeff, ratXCoeff, tmpCoeffDegX, tmpCoeffDegY, ratXCoeffDegX, ratXCoeffDegY);
                tmpCoeffDegX += ratXCoeffDegX;
                tmpCoeffDegY += ratXCoeffDegY;
            }
            for (int i = 0; i <= tmpCoeffDegX; i++) {
                for (int j = 0; j <= tmpCoeffDegY; j++) {
                    newCoeff[i][j] += tmpCoeff[i][j];
                    tmpCoeff[i][j] = 0;
                }
            }
            newCoeffDegX = Math.max(newCoeffDegX, tmpCoeffDegX);
            newCoeffDegY = Math.max(newCoeffDegY, tmpCoeffDegY);
            tmpCoeffDegX = 0;
            tmpCoeffDegY = 0;
            if (x > 0) {
                polyMult(newCoeff, pX, newCoeffDegX, newCoeffDegY, degXpX, degYpX);
                newCoeffDegX += degXpX;
                newCoeffDegY += degYpX;
            }
        }
        //maybe we made the degree larger than necessary, so we try to get it down.
        coeff = PolynomialUtils.coeffMinDeg(newCoeff);
        //calculate new degree
        degX = coeff.length - 1;
        degY = 0;
        for (int i = 0; i < coeff.length; i++) {
            degY = Math.max(degY, coeff[i].length - 1);
        }

        setValidInputForm(false); //we changed the polynomial => not the same as the userInput
        updatePath();
        if (algoUpdateSet != null) {
            double a = 0, ax = 0, ay = 0, b = 0, bx = 0, by = 0;
            if (qX == null && qY == null && degXpX <= 1 && degYpX <= 1 && degXpY <= 1 && degYpY <= 1) {
                if ((degXpX != 1 || degYpX != 1 || pX[1].length == 1 || Kernel.isZero(pX[1][1]))
                        && (degXpY != 1 || degYpY != 1 || pY[1].length == 1 || Kernel.isZero(pY[1][1]))) {
                    if (pX.length > 0) {
                        if (pX[0].length > 0) {
                            a = pX[0][0];
                        }
                        if (pX[0].length > 1) {
                            ay = pX[0][1];
                        }
                    }
                    if (pX.length > 1) {
                        ax = pX[1][0];
                    }
                    if (pY.length > 0) {
                        if (pY[0].length > 0) {
                            b = pY[0][0];
                        }
                        if (pY[0].length > 1) {
                            by = pY[0][1];
                        }
                    }
                    if (pY.length > 1) {
                        bx = pY[1][0];
                    }
                    double det = ax * by - bx * ay;
                    if (!Kernel.isZero(det)) {
                        double[][] iX = new double[][] { { (b * ay - a * by) / det, -ay / det }, { by / det } };
                        double[][] iY = new double[][] { { -(b * ax - a * bx) / det, ax / det }, { -bx / det } };

                        Iterator<AlgoElement> it = algoUpdateSet.getIterator();
                        while (it != null && it.hasNext()) {
                            AlgoElement elem = it.next();
                            if (elem instanceof AlgoPointOnPath && isIndependent()) {
                                GeoPoint point = ((AlgoPointOnPath) elem).getP();
                                if (!Kernel.isZero(point.getZ())) {
                                    double x = point.getX() / point.getZ();
                                    double y = point.getY() / point.getZ();
                                    double px = evalPolyCoeffAt(x, y, iX);
                                    double py = evalPolyCoeffAt(x, y, iY);
                                    point.setCoords(px, py, 1);
                                    point.updateCoords();
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    public void plugInPoly(double[][] polyX, double[][] polyY) {
        plugInRatPoly(polyX, polyY, null, null);
    }

    /**
     * 
     * @param polyDest
     * @param polySrc
     * polyDest=polyDest*polySrc;
     */
    private static void polyMult(double[][] polyDest, double[][] polySrc, int degDestX, int degDestY, int degSrcX,
            int degSrcY) {
        double[][] result = new double[degDestX + degSrcX + 1][degDestY + degSrcY + 1];
        for (int n = 0; n <= degDestX + degSrcX; n++) {
            for (int m = 0; m <= degDestY + degSrcY; m++) {
                double sum = 0;
                for (int k = Math.max(0, n - degSrcX); k <= Math.min(n, degDestX); k++)
                    for (int j = Math.max(0, m - degSrcY); j <= Math.min(m, degDestY); j++)
                        sum += polyDest[k][j] * polySrc[n - k][m - j];
                result[n][m] = sum;
            }
        }
        for (int n = 0; n <= degDestX + degSrcX; n++) {
            for (int m = 0; m <= degDestY + degSrcY; m++) {
                polyDest[n][m] = result[n][m];
            }
        }
    }

    public boolean isConstant() {
        return isConstant;
    }

    public int getDegX() {
        return degX;
    }

    public int getDegY() {
        return degY;
    }

    private void getFactors() {

    }

    final public double distance(GeoPoint p) {
        AlgoClosestPoint algo = new AlgoClosestPoint(cons, "", this, p);
        algo.remove();
        GeoPoint pointOnCurve = (GeoPoint) algo.getP();
        return p.distance(pointOnCurve);
    }

    /** 
     * Makes make curve through given points 
     * @param points array of points
     */
    public void throughPoints(GeoPoint[] points) {
        ArrayList<GeoPoint> p = new ArrayList<GeoPoint>();
        for (int i = 0; i < points.length; i++)
            p.add(points[i]);
        throughPoints(p);
    }

    /** 
     * Makes make curve through given points 
     * @param points array of points
     */
    public void throughPoints(GeoList points) {
        ArrayList<GeoPoint> p = new ArrayList<GeoPoint>();
        for (int i = 0; i < points.size(); i++)
            p.add((GeoPoint) points.get(i));
        throughPoints(p);
    }

    /**
     * make curve through given points
     * @param points ArrayList of points
     */
    public void throughPoints(ArrayList<GeoPoint> points) {
        if ((int) Math.sqrt(9 + 8 * points.size()) != Math.sqrt(9 + 8 * points.size())) {
            setUndefined();
            return;
        }

        int degree = (int) (0.5 * Math.sqrt(8 * (1 + points.size()))) - 1;
        int realDegree = degree;

        RealMatrix extendMatrix = new RealMatrixImpl(points.size(), points.size() + 1);
        RealMatrix matrix = new RealMatrixImpl(points.size(), points.size());
        double[][] coeffMatrix = new double[degree + 1][degree + 1];

        DecompositionSolver solver;

        double[] matrixRow = new double[points.size() + 1];
        double[] results;

        for (int i = 0; i < points.size(); i++) {
            double x = points.get(i).x / points.get(i).z;
            double y = points.get(i).y / points.get(i).z;

            for (int j = 0, m = 0; j < degree + 1; j++)
                for (int k = 0; j + k != degree + 1; k++)
                    matrixRow[m++] = Math.pow(x, j) * Math.pow(y, k);
            extendMatrix.setRow(i, matrixRow);
        }

        int solutionColumn = 0, noPoints = points.size();

        do {
            if (solutionColumn > noPoints) {
                noPoints = noPoints - realDegree - 1;

                if (noPoints < 2) {
                    setUndefined();
                    return;
                }

                extendMatrix = new RealMatrixImpl(noPoints, noPoints + 1);
                realDegree -= 1;
                matrixRow = new double[noPoints + 1];

                for (int i = 0; i < noPoints; i++) {
                    double x = points.get(i).x;
                    double y = points.get(i).y;

                    for (int j = 0, m = 0; j < realDegree + 1; j++)
                        for (int k = 0; j + k != realDegree + 1; k++)
                            matrixRow[m++] = Math.pow(x, j) * Math.pow(y, k);
                    extendMatrix.setRow(i, matrixRow);
                }

                matrix = new RealMatrixImpl(noPoints, noPoints);
                solutionColumn = 0;
            }

            results = extendMatrix.getColumn(solutionColumn);

            for (int i = 0, j = 0; i < noPoints + 1; i++)
                if (i == solutionColumn)
                    continue;
                else
                    matrix.setColumn(j++, extendMatrix.getColumn(i));
            solutionColumn++;

            solver = new LUDecompositionImpl(matrix).getSolver();
        } while (!solver.isNonSingular());

        for (int i = 0; i < results.length; i++)
            results[i] *= -1;

        double[] partialSolution = solver.solve(results);

        double[] solution = new double[partialSolution.length + 1];

        for (int i = 0, j = 0; i < solution.length; i++)
            if (i == solutionColumn - 1)
                solution[i] = 1;
            else {
                solution[i] = (Kernel.isZero(partialSolution[j])) ? 0 : partialSolution[j];
                j++;
            }

        for (int i = 0, k = 0; i < realDegree + 1; i++)
            for (int j = 0; i + j < realDegree + 1; j++)
                coeffMatrix[i][j] = solution[k++];

        this.setCoeff(coeffMatrix, true);

        this.defined = true;
        for (int i = 0; i < points.size(); i++)
            if (!this.isOnPath(points.get(i), 1)) {
                this.setUndefined();
                return;
            }

    }

    protected void polishPointOnPath(GeoPointND PI) {
        PI.updateCoords2D();
        double x = PI.getX2D();
        double y = PI.getY2D();

        double dx, dy;
        dx = evalDiffXPolyAt(x, y);
        dy = evalDiffYPolyAt(x, y);
        double d = Math.abs(dx) + Math.abs(dy);
        if (Kernel.isZero(d))
            return;
        dx /= d;
        dy /= d;
        double[] pair = new double[] { x, y };
        double[] line = new double[] { y * dx - x * dy, dy, -dx };
        if (PolynomialUtils.rootPolishing(pair, this, line)) {
            PI.setCoords2D(pair[0], pair[1], 1);
        }
    }

    public void pointChanged(GeoPointND PI) {
        if (locus.getPoints().size() > 0) {
            locus.pointChanged(PI);
            polishPointOnPath(PI);
        }
    }

    public void pathChanged(GeoPointND PI) {
        if (locus.getPoints().size() > 0) {
            locus.pathChanged(PI);
            polishPointOnPath(PI);
        }
    }

    public boolean isOnPath(GeoPointND PI) {
        return isOnPath(PI, Kernel.STANDARD_PRECISION);
    }

    public boolean isOnPath(GeoPointND PI, double eps) {

        if (!PI.isDefined())
            return false;

        GeoPoint P = (GeoPoint) PI;

        double px = P.x;
        double py = P.y;
        double pz = P.z;

        if (P.isFinite()) {
            px /= pz;
            py /= pz;
        }

        double value = this.evalPolyAt(px, py);

        return Math.abs(value) < Kernel.MIN_PRECISION;
    }

    public double getMinParameter() {
        return locus.getMinParameter();
    }

    public double getMaxParameter() {
        return locus.getMaxParameter();
    }

    public boolean isClosedPath() {
        return locus.isClosedPath();
    }

    public PathMover createPathMover() {
        return locus.createPathMover();
    }

    //traceable

    public boolean isTraceable() {
        return true;
    }

    public void setTrace(boolean trace) {
        this.trace = trace;
    }

    public boolean getTrace() {
        return trace;
    }

    /**
     * Return degree of implicit poly (x^n y^m = 1 has degree of m+n)
     * @return degree of implicit poly
     */
    public int getDeg() {
        int deg = 0;
        for (int d = degX + degY; d >= 0; d--) {
            for (int x = 0; x <= degX; x++) {
                int y = d - x;
                if (y >= 0 && y < coeff[x].length) {
                    if (Math.abs(coeff[x][y]) > Kernel.EPSILON) {
                        deg = d;
                        d = 0;
                        break;
                    }
                }
            }
        }
        return deg;
    }

    public void mirror(GeoConic c) {

        if (c.getCircleRadius() < 10e-2) {
            setUndefined();
            return;
        }

        double cx = c.getMidpoint().getX();
        double cy = c.getMidpoint().getY();
        double cr = c.getCircleRadius();

        plugInRatPoly(
                new double[][] { { cx * cx * cx + cx * cy * cy - cx * cr * cr, -2 * cx * cy, cx },
                        { -2 * cx * cx + cr * cr, 0, 0 }, { cx, 0, 0 } },
                new double[][] { { cx * cx * cy + cy * cy * cy - cy * cr * cr, -2 * cy * cy + cr * cr, cy },
                        { -2 * cx * cy, 0, 0 }, { cy, 0, 0 } },
                new double[][] { { cx * cx + cy * cy, -2 * cy, 1 }, { -2 * cx, 0, 0 }, { 1, 0, 0 } },
                new double[][] { { cx * cx + cy * cy, -2 * cy, 1 }, { -2 * cx, 0, 0 }, { 1, 0, 0 } });
    }

    public void mirror(GeoPoint Q) {
        plugInPoly(new double[][] { { 2 * Q.inhomX }, { -1 } }, new double[][] { { 2 * Q.inhomY, -1 } });
    }

    public void mirror(GeoLine g) {
        if (!g.isDefined()) {
            setUndefined();
            return;
        }
        double[] dir = new double[2];
        g.getDirection(dir);
        double dx = dir[0];
        double dy = dir[1];
        double x = g.getStartPoint().inhomX;
        double y = g.getStartPoint().inhomY;
        double n = 1 / (dx * dx + dy * dy);
        plugInPoly(
                new double[][] { { 2 * n * dy * (x * dy - y * dx), 2 * n * dx * dy }, { 1 - 2 * dy * dy * n, 0 } },
                new double[][] { { 2 * n * dx * (y * dx - x * dy), 1 - 2 * n * dx * dx }, { 2 * n * dx * dy, 0 } });

    }

    public void translate(Coords v) {
        translate(v.getX(), v.getY());
    }

    public void translate(double vx, double vy) {
        double a = -vx; //-translate in X-dir
        double b = -vy; //-translate in Y-dir
        plugInPoly(new double[][] { { a }, { 1 } }, new double[][] { { b, 1 } });
    }

    public void rotate(NumberValue phiValue) {
        double phi = phiValue.getDouble();
        double cos = Math.cos(phi);
        double sin = Math.sin(-phi);
        plugInPoly(new double[][] { { 0, -sin }, { cos, 0 } }, new double[][] { { 0, cos }, { sin, 0 } });
    }

    public void rotate(NumberValue phiValue, GeoPoint S) {
        double phi = phiValue.getDouble();
        double cos = Math.cos(phi);
        double sin = Math.sin(-phi);
        double x = S.getInhomX();
        double y = S.getInhomY();
        plugInPoly(new double[][] { { x * (1 - cos) + y * sin, -sin }, { cos, 0 } },
                new double[][] { { -x * sin + y * (1 - cos), cos }, { sin, 0 } });
    }

    public void dilate(NumberValue rval, GeoPoint S) {
        double r = 1 / rval.getDouble();
        plugInPoly(new double[][] { { (1 - r) * S.getInhomX() }, { r } },
                new double[][] { { (1 - r) * S.getInhomY(), r } });
    }

    @Override
    public boolean isTranslateable() {
        return true;
    }

    @Override
    protected char getLabelDelimiter() {
        return ':';
    }

    /*
     * Calculation of the points on the curve.
     * Mainly used for drawing, but also for Implementation of Path-Interface
     * Was part of DrawImplicitPoly.
     */

    public boolean euclidianViewUpdate() {
        if (getDefined()) {
            updatePath();
            return true;
        }
        return false;
    }

    /**
     * X and Y of the point on the curve next to the Right Down Corner of the View, for the Label
     */
    private List<double[]> singularitiesCollection;
    private List<double[]> boundaryIntersectCollection;

    //Second Algorithm
    final public static double EPS = Kernel.EPSILON;

    /**
     * @param x
     * @return 0 if |x| &lt EPS, sgn(x) otherwise
     */
    public int epsSignum(double x) {
        if (x > EPS)
            return 1;
        if (x < -EPS)
            return -1;
        return 0;
    }

    private static class GridRect {
        double x, y, width, height;
        int[] eval;

        public GridRect(double x, double y, double width, double height) {
            super();
            this.x = x;
            this.y = y;
            this.width = width;
            this.height = height;
            eval = new int[4];
        }
    }

    private boolean[][] remember;
    private GridRect[][] grid;

    private int gridWidth = 30; //grid"Resolution" how many grids in one row
    private int gridHeight = 30; //how many grids in one col

    private double scaleX;
    private double scaleY;

    private double minGap = 0.001;

    /**
     * updates the path inside the current view-rectangle
     */
    public void updatePath() {
        double[] viewBounds = kernel.getViewBoundsForGeo(this);
        if (viewBounds[0] == Double.POSITIVE_INFINITY) { //no active View
            viewBounds = new double[] { -10, 10, -10, 10, 10, 10 }; //get some value...
        }
        updatePath(viewBounds[0], viewBounds[2], viewBounds[1] - viewBounds[0], viewBounds[3] - viewBounds[2],
                1. / viewBounds[4] / viewBounds[5]);
    }

    /**
     * Calculates the path of the curve inside the given rectangle.
     * @param rectX X of lower left corner
     * @param rectY Y of lower left corner
     * @param rectW width of rect
     * @param rectH height of rect
     * @param resolution gives the area covered by one "pixel" of the screen
     */
    public void updatePath(double rectX, double rectY, double rectW, double rectH, double resolution) {
        if (!calcPath) //important for helper curves, which aren't visible
            return;
        locus.clearPoints();
        singularitiesCollection = new ArrayList<double[]>();
        boundaryIntersectCollection = new ArrayList<double[]>();

        grid = new GridRect[gridWidth][gridHeight];
        remember = new boolean[gridWidth][gridHeight];

        double prec = 5;
        scaleX = prec * Math.sqrt(resolution);
        scaleY = prec * Math.sqrt(resolution);

        double grw = rectW / gridWidth;
        double grh = rectH / gridHeight;
        double x = rectX;
        int e;
        for (int w = 0; w < gridWidth; w++) {
            double y = rectY;
            for (int h = 0; h < gridHeight; h++) {
                e = epsSignum(evalPolyAt(x, y, true));
                grid[w][h] = new GridRect(x, y, grw, grh);
                grid[w][h].eval[0] = e;
                if (w > 0) {
                    grid[w - 1][h].eval[1] = e;
                    if (h > 0) {
                        grid[w][h - 1].eval[2] = e;
                        grid[w - 1][h - 1].eval[3] = e;
                    }
                } else if (h > 0)
                    grid[w][h - 1].eval[2] = e;
                y += grh;
            }
            e = epsSignum(evalPolyAt(x, y, true));
            grid[w][gridHeight - 1].eval[2] = e;
            if (w > 0)
                grid[w - 1][gridHeight - 1].eval[3] = e;
            x += grw;
        }
        double y = rectY;
        for (int h = 0; h < gridHeight; h++) {
            e = epsSignum(evalPolyAt(x, y, true));
            grid[gridWidth - 1][h].eval[1] = e;
            if (h > 0)
                grid[gridWidth - 1][h - 1].eval[3] = e;
            y += grh;
        }
        grid[gridWidth - 1][gridHeight - 1].eval[3] = epsSignum(evalPolyAt(x, y, true));
        for (int w = 0; w < gridWidth; w++) {
            for (int h = 0; h < gridHeight; h++) {
                remember[w][h] = false;
                if (grid[w][h].eval[0] == 0) {
                    remember[w][h] = true;
                    continue;
                }
                for (int i = 1; i < 4; i++) {
                    if (grid[w][h].eval[0] != grid[w][h].eval[i]) {
                        remember[w][h] = true;
                        break;
                    }
                }
            }
        }
        //         gps=new ArrayList<GeneralPath>();
        //         EuclidianView v=kernel.getApplication().getEuclidianView();
        //         Graphics2D g2=(Graphics2D) v.getGraphics();
        //         for (int w=0;w<gridWidth;w++)
        //            for (int h=0;h<gridHeight;h++){
        //               int sx=v.toScreenCoordX(grid[w][h].x);
        //               int sy=v.toScreenCoordY(grid[w][h].y);
        //               for (int i=0;i<4;i++){
        //                  Color c=Color.black;
        //                  if (grid[w][h].eval[i]<0){
        //                     c=Color.green;
        //                  }else if (grid[w][h].eval[i]>0){
        //                     c=Color.red;
        //                  }
        //                  g2.setColor(c);
        //                  g2.fillOval(sx+(i%2==0?-3:3), sy+(i<2?3:-3), 2, 2);
        //               }
        //            }
        for (int w = 0; w < gridWidth; w++) {
            for (int h = 0; h < gridHeight; h++) {
                if (remember[w][h]) {
                    if (grid[w][h].eval[0] == 0) {
                        startPath(w, h, grid[w][h].x, grid[w][h].y, locus);
                    } else {
                        double xs, ys;
                        if (grid[w][h].eval[0] != grid[w][h].eval[3]) {
                            double a = bisec(grid[w][h].x, grid[w][h].y, grid[w][h].x + grid[w][h].width,
                                    grid[w][h].y + grid[w][h].height);
                            xs = grid[w][h].x + a * grid[w][h].width;
                            ys = grid[w][h].y + a * grid[w][h].height;
                        } else if (grid[w][h].eval[1] != grid[w][h].eval[2]) {
                            double a = bisec(grid[w][h].x + grid[w][h].width, grid[w][h].y, grid[w][h].x,
                                    grid[w][h].y + grid[w][h].height);
                            xs = grid[w][h].x + (1 - a) * grid[w][h].width;
                            ys = grid[w][h].y + a * grid[w][h].height;
                        } else {
                            double a = bisec(grid[w][h].x, grid[w][h].y, grid[w][h].x + grid[w][h].width,
                                    grid[w][h].y);
                            xs = grid[w][h].x + a * grid[w][h].width;
                            ys = grid[w][h].y;
                        }
                        startPath(w, h, xs, ys, locus);
                    }
                }
            }
        }
        if (algoUpdateSet != null) {
            Iterator<AlgoElement> it = algoUpdateSet.getIterator();
            while (it.hasNext()) {
                AlgoElement elem = it.next();
                if (elem instanceof AlgoPointOnPath) {
                    for (int i = 0; i < elem.getInput().length; i++) {
                        if (elem.getInput()[i] == this) {
                            AlgoPointOnPath ap = (AlgoPointOnPath) elem;
                            if (ap.getPath() == this) {
                                ap.getP().setCoords(ap.getP().getCoords(), true);
                            }
                            break;
                        }
                    }
                }
            }
        }

    }

    private final static double MIN_GRAD = Kernel.STANDARD_PRECISION;
    private final static double MIN_STEP_SIZE = 0.1; //Pixel on Screen
    private final static double START_STEP_SIZE = 0.5;
    private final static double MAX_STEP_SIZE = 1;
    private final static double MIN_PATH_GAP = 1;
    private final static double SING_RADIUS = 1;
    private final static double NEAR_SING = 1E-3;

    private double scaledNormSquared(double x, double y) {
        return x * x / scaleX / scaleX + y * y / scaleY / scaleY;
    }

    private void startPath(int w, int h, double x, double y, GeoLocus locus) {

        double sx = x;
        double sy = y;
        double lx = Double.NaN; //no previous point
        double ly = Double.NaN;
        boolean first = true;

        double stepSize = START_STEP_SIZE * Math.max(scaleX, scaleY);
        double startX = x;
        double startY = y;

        ArrayList<MyPoint> firstDirPoints = new ArrayList<MyPoint>();
        firstDirPoints.add(new MyPoint(x, y, true));

        int s = 0;
        int lastW = w;
        int lastH = h;
        int startW = w;
        int startH = h;
        int stepCount = 0;
        boolean nearSing = false;
        double lastGradX = Double.POSITIVE_INFINITY;
        double lastGradY = Double.POSITIVE_INFINITY;
        while (true) {
            s++;
            boolean reachedSingularity = false;
            boolean reachedEnd = false;
            if (!Double.isNaN(lx) && !Double.isNaN(ly)) {
                if ((scaledNormSquared(startX - sx, startY - sy) < MAX_STEP_SIZE * MAX_STEP_SIZE)
                        && (scaledNormSquared(startX - sx, startY - sy) < scaledNormSquared(startX - lx,
                                startY - ly))) {
                    /* loop found */
                    if (firstDirPoints != null) {
                        MyPoint firstPoint = firstDirPoints.get(0);
                        firstPoint.lineTo = false;
                        locus.getPoints().addAll(firstDirPoints);
                    }
                    locus.insertPoint(x, y, true);
                    return;
                }
            }
            while (sx < grid[w][h].x) {
                if (w > 0)
                    w--;
                else {
                    reachedEnd = true;
                    break;
                }
            }
            while (sx > grid[w][h].x + grid[w][h].width) {
                if (w < grid.length - 1)
                    w++;
                else {
                    reachedEnd = true;
                    break;
                }
            }
            while (sy < grid[w][h].y) {
                if (h > 0)
                    h--;
                else {
                    reachedEnd = true;
                    break;
                }
            }
            while (sy > grid[w][h].y + grid[w][h].height) {
                if (h < grid[w].length - 1)
                    h++;
                else {
                    reachedEnd = true;
                    break;
                }
            }
            if (reachedEnd) { //we reached the boundary
                boundaryIntersectCollection.add(new double[] { sx, sy });
            }
            if (lastW != w || lastH != h) {
                int dw = (int) Math.signum(lastW - w);
                int dh = (int) Math.signum(lastH - h);
                for (int i = 0; i <= Math.abs(lastW - w); i++) {
                    for (int j = 0; j <= Math.abs(lastH - h); j++) {
                        remember[lastW - dw * i][lastH - dh * j] = false;
                    }
                }
            }
            lastW = w;
            lastH = h;

            double gradX = 0;
            double gradY = 0;
            if (!reachedEnd) {
                gradX = evalDiffXPolyAt(sx, sy, true);
                gradY = evalDiffYPolyAt(sx, sy, true);

                /*
                 * Dealing with singularities: tries to reach the singularity but stops there.
                 * Assuming that the singularity is on or at least near the curve. (Since first
                 * derivative is zero this can be assumed for 'nice' 2nd derivative)
                 */

                if (nearSing || (Math.abs(gradX) < NEAR_SING && Math.abs(gradY) < NEAR_SING)) {
                    for (double[] pair : singularitiesCollection) { //check if this singularity is already known
                        if ((scaledNormSquared(pair[0] - sx, pair[1] - sy) < SING_RADIUS * SING_RADIUS)) {
                            sx = pair[0];
                            sy = pair[1];
                            reachedSingularity = true;
                            reachedEnd = true;
                            break;
                        }
                    }
                    if (!reachedEnd) {
                        if (gradX * gradX + gradY * gradY > lastGradX * lastGradX + lastGradY * lastGradY) { //going away from the singularity, stop here
                            singularitiesCollection.add(new double[] { sx, sy });
                            reachedEnd = true;
                            reachedSingularity = true;
                        } else if (Math.abs(gradX) < MIN_GRAD && Math.abs(gradY) < MIN_GRAD) { //singularity
                            singularitiesCollection.add(new double[] { sx, sy });
                            reachedEnd = true;
                            reachedSingularity = true;
                        }
                        lastGradX = gradX;
                        lastGradY = gradY;
                        nearSing = true;
                    }
                }
            }
            double a = 0, nX = 0, nY = 0;
            if (!reachedEnd) {
                a = 1 / (Math.abs(gradX) + Math.abs(gradY)); //trying to increase numerical stability
                gradX = a * gradX;
                gradY = a * gradY;
                a = Math.sqrt(gradX * gradX + gradY * gradY);
                gradX = gradX / a; //scale vector
                gradY = gradY / a;
                nX = -gradY;
                nY = gradX;
                if (!Double.isNaN(lx) && !Double.isNaN(ly)) {
                    double c = (lx - sx) * nX + (ly - sy) * nY;
                    if (c > 0) {
                        nX = -nX;
                        nY = -nY;
                    }
                } else {
                    if (!first) { //other dir now
                        nX = -nX;
                        nY -= nY;
                    }
                }
                lx = sx;
                ly = sy;
            }
            while (!reachedEnd) {
                sx = lx + nX * stepSize; //go in "best" direction
                sy = ly + nY * stepSize;
                int e = epsSignum(evalPolyAt(sx, sy, true));
                if (e == 0) {
                    if (stepSize * 2 <= MAX_STEP_SIZE * Math.max(scaleX, scaleY))
                        stepSize *= 2;
                    break;
                } else {
                    gradX = evalDiffXPolyAt(sx, sy, true);
                    gradY = evalDiffYPolyAt(sx, sy, true);
                    if (Math.abs(gradX) < MIN_GRAD && Math.abs(gradY) < MIN_GRAD) { //singularity
                        stepSize /= 2;
                        if (stepSize > MIN_STEP_SIZE * Math.max(scaleX, scaleY))
                            continue;
                        else {
                            singularitiesCollection.add(new double[] { sx, sy });
                            reachedEnd = true;
                            break;
                        }
                    }
                    a = Math.sqrt(gradX * gradX + gradY * gradY);
                    gradX *= stepSize / a;
                    gradY *= stepSize / a;
                    if (e > 0) {
                        gradX = -gradX;
                        gradY = -gradY;
                    }
                    int e1 = epsSignum(evalPolyAt(sx + gradX, sy + gradY, true));
                    if (e1 == 0) {
                        sx = sx + gradX;
                        sy = sy + gradY;
                        break;
                    }
                    if (e1 != e) {
                        a = bisec(sx, sy, sx + gradX, sy + gradY);
                        sx += a * gradX;
                        sy += a * gradY;
                        break;
                    } else {
                        stepSize /= 2;
                        if (stepSize > MIN_STEP_SIZE * Math.max(scaleX, scaleY))
                            continue;
                        else {
                            reachedEnd = true;
                            break;
                        }
                    }
                }
            }
            if (!reachedEnd || reachedSingularity) {
                if (reachedSingularity || ((lx - sx) * (lx - sx) + (ly - sy) * (ly - sy) > minGap * minGap)) {
                    if (firstDirPoints != null) {
                        firstDirPoints.add(new MyPoint(sx, sy, true));
                    } else {
                        locus.insertPoint(sx, sy, true);
                    }
                    stepCount++;
                }
            }
            if (reachedEnd) {
                if (!first) {
                    return; //reached the end two times
                }
                lastGradX = Double.POSITIVE_INFINITY;
                lastGradY = Double.POSITIVE_INFINITY;

                /* we reached end for the first time and now save the points into the locus */
                ArrayList<MyPoint> pointList = locus.getMyPointList();
                if (firstDirPoints.size() > 0) {
                    MyPoint lastPoint = firstDirPoints.get(firstDirPoints.size() - 1);
                    lastPoint.lineTo = false;
                    pointList.ensureCapacity(pointList.size() + firstDirPoints.size());
                    for (int i = firstDirPoints.size() - 1; i >= 0; i--) {
                        pointList.add(firstDirPoints.get(i));
                    }
                }
                firstDirPoints = null;
                sx = startX;
                sy = startY;
                lx = Double.NaN;
                ly = Double.NaN;
                w = startW;
                h = startH;
                lastW = w;
                lastH = h;
                first = false;//start again with other direction
                reachedEnd = false;
                reachedSingularity = false;
                nearSing = false;
            }
        }
    }

    /**
     * 
     * @param x1
     * @param y1
     * @param x2
     * @param y2
     * @return a such that |f(x1+(x2-x1)*a,y1+(y2-y1)*a)| &lt eps
     */
    public double bisec(double x1, double y1, double x2, double y2) {
        int e1 = epsSignum(evalPolyAt(x1, y1, true));
        int e2 = epsSignum(evalPolyAt(x2, y2, true));
        if (e1 == 0)
            return 0.;
        if (e2 == 0)
            return 1.;
        double a1 = 0;
        double a2 = 1;
        int e;
        if (e1 != e2) {
            //solved #278 PRECISION to small (was Double.MIN_VALUE)
            while (a2 - a1 > Kernel.MAX_PRECISION) {
                e = epsSignum(evalPolyAt(x1 + (x2 - x1) * (a2 + a1) / 2, y1 + (y2 - y1) * (a2 + a1) / 2, true));
                if (e == 0) {
                    return (a2 + a1) / 2;
                }
                if (e == e1) {
                    a1 = (a2 + a1) / 2;
                } else {
                    a2 = (a1 + a2) / 2;
                }
            }
            return (a1 + a2) / 2;
        }
        return Double.NaN;
    }

}