/****************************************************************************+
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**+
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** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).+
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** All rights reserved.+
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** Contact: Nokia Corporation (qt-info@nokia.com)+
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**+
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** This file is part of the QtGui module of the Qt Toolkit.+
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**+
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** $QT_BEGIN_LICENSE:LGPL$+
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** No Commercial Usage+
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** This file contains pre-release code and may not be distributed.+
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** You may use this file in accordance with the terms and conditions+
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** contained in the Technology Preview License Agreement accompanying+
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** this package.+
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**+
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** GNU Lesser General Public License Usage+
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** Alternatively, this file may be used under the terms of the GNU Lesser+
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** General Public License version 2.1 as published by the Free Software+
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** Foundation and appearing in the file LICENSE.LGPL included in the+
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** packaging of this file.  Please review the following information to+
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** ensure the GNU Lesser General Public License version 2.1 requirements+
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** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.+
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**+
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** In addition, as a special exception, Nokia gives you certain additional+
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** rights.  These rights are described in the Nokia Qt LGPL Exception+
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** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.+
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**+
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** If you have questions regarding the use of this file, please contact+
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** Nokia at qt-info@nokia.com.+
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** $QT_END_LICENSE$+
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**+
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****************************************************************************/+
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+
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#ifndef QSIMPLEX_P_H+
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#define QSIMPLEX_P_H+
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+
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//+
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//  W A R N I N G+
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//  -------------+
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//+
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// This file is not part of the Qt API.  It exists purely as an+
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// implementation detail.  This header file may change from version to+
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// version without notice, or even be removed.+
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//+
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// We mean it.+
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//+
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+
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#include <QtCore/qhash.h>+
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#include <QtCore/qpair.h>+
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+
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QT_BEGIN_NAMESPACE+
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+
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struct QSimplexVariable+
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{+
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    QSimplexVariable() : result(0), index(0) {}+
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+
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    qreal result;+
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    int index;+
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};+
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+
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+
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/*!+
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  \internal+
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+
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  Representation of a LP constraint like:+
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+
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    (c1 * X1) + (c2 * X2) + ...  =  K+
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                             or <=  K+
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                             or >=  K+
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+
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    Where (ci, Xi) are the pairs in "variables" and K the real "constant".+
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*/+
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struct QSimplexConstraint+
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{+
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    QSimplexConstraint() : constant(0), ratio(Equal), artificial(0) {}+
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+
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    enum Ratio {+
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        LessOrEqual = 0,+
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        Equal,+
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        MoreOrEqual+
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    };+
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+
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    QHash<QSimplexVariable *, qreal> variables;+
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    qreal constant;+
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    Ratio ratio;+
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+
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    QPair<QSimplexVariable *, qreal> helper;+
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    QSimplexVariable * artificial;+
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+
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    void invert();+
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+
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    bool isSatisfied() {+
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        qreal leftHandSide(0);+
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+
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        QHash<QSimplexVariable *, qreal>::const_iterator iter;+
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        for (iter = variables.constBegin(); iter != variables.constEnd(); ++iter) {+
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            leftHandSide += iter.value() * iter.key()->result;+
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        }+
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+
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        Q_ASSERT(constant > 0 || qFuzzyCompare(1, 1 + constant));+
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+
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        if ((leftHandSide == constant) || qAbs(leftHandSide - constant) < 0.0000001)+
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            return true;+
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+
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        switch (ratio) {+
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        case LessOrEqual:+
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            return leftHandSide < constant;+
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        case MoreOrEqual:+
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            return leftHandSide > constant;+
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        default:+
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            return false;+
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        }+
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    }+
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+
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#ifdef QT_DEBUG+
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    QString toString() {+
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        QString result;+
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        result += QString::fromAscii("-- QSimplexConstraint %1 --").arg(quintptr(this), 0, 16);+
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+
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        QHash<QSimplexVariable *, qreal>::const_iterator iter;+
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        for (iter = variables.constBegin(); iter != variables.constEnd(); ++iter) {+
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            result += QString::fromAscii("  %1 x %2").arg(iter.value()).arg(quintptr(iter.key()), 0, 16);+
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        }+
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+
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        switch (ratio) {+
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        case LessOrEqual:+
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            result += QString::fromAscii("  (less) <= %1").arg(constant);+
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            break;+
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        case MoreOrEqual:+
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            result += QString::fromAscii("  (more) >= %1").arg(constant);+
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            break;+
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        default:+
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            result += QString::fromAscii("  (eqal) == %1").arg(constant);+
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        }+
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+
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        return result;+
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    }+
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#endif+
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};+
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+
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class QSimplex+
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{+
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public:+
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    QSimplex();+
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    virtual ~QSimplex();+
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+
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    qreal solveMin();+
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    qreal solveMax();+
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+
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    bool setConstraints(const QList<QSimplexConstraint *> constraints);+
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    void setObjective(QSimplexConstraint *objective);+
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+
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    void dumpMatrix();+
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+
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private:+
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    // Matrix handling+
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    qreal valueAt(int row, int column);+
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    void setValueAt(int row, int column, qreal value);+
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    void clearRow(int rowIndex);+
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    void clearColumns(int first, int last);+
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    void combineRows(int toIndex, int fromIndex, qreal factor);+
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+
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    // Simplex+
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    bool simplifyConstraints(QList<QSimplexConstraint *> *constraints);+
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    int findPivotColumn();+
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    int pivotRowForColumn(int column);+
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    void reducedRowEchelon();+
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    bool iterate();+
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+
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    // Helpers+
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    void clearDataStructures();+
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    void solveMaxHelper();+
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    enum solverFactor { Minimum = -1, Maximum = 1 };+
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    qreal solver(solverFactor factor);+
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    void collectResults();+
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+
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    QList<QSimplexConstraint *> constraints;+
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    QList<QSimplexVariable *> variables;+
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    QSimplexConstraint *objective;+
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+
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    int rows;+
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    int columns;+
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    int firstArtificial;+
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+
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    qreal *matrix;+
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};+
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+
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inline qreal QSimplex::valueAt(int rowIndex, int columnIndex)+
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{+
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    return matrix[rowIndex * columns + columnIndex];+
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}+
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+
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inline void QSimplex::setValueAt(int rowIndex, int columnIndex, qreal value)+
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{+
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    matrix[rowIndex * columns + columnIndex] = value;+
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}+
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+
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QT_END_NAMESPACE+
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+
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#endif // QSIMPLEX_P_H+
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