calculator.h Example File
widgets/calculator/calculator.h
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    ** Copyright (C) 2005-2006 Trolltech AS. All rights reserved.
    **
    ** This file is part of the documentation of the Qt Toolkit.
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    ** and appearing in the file LICENSE.GPL included in the packaging of
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    #ifndef CALCULATOR_H
    #define CALCULATOR_H
    #include <QDialog>
    class QLineEdit;
    class Button;
    class Calculator : public QDialog
    {
        Q_OBJECT
    public:
        Calculator(QWidget *parent = 0);
    protected:
        bool eventFilter(QObject *target, QEvent *event);
    private slots:
        void digitClicked();
        void unaryOperatorClicked();
        void additiveOperatorClicked();
        void multiplicativeOperatorClicked();
        void equalClicked();
        void pointClicked();
        void changeSignClicked();
        void backspaceClicked();
        void clear();
        void clearAll();
        void clearMemory();
        void readMemory();
        void setMemory();
        void addToMemory();
    private:
        Button *createButton(const QString &text, const QColor &color,
                             const char *member);
        void abortOperation();
        bool calculate(double rightOperand, const QString &pendingOperator);
        double sumInMemory;
        double sumSoFar;
        double factorSoFar;
        QString pendingAdditiveOperator;
        QString pendingMultiplicativeOperator;
        bool waitingForOperand;
        QLineEdit *display;
        enum { NumDigitButtons = 10 };
        Button *digitButtons[NumDigitButtons];
        Button *pointButton;
        Button *changeSignButton;
        Button *backspaceButton;
        Button *clearButton;
        Button *clearAllButton;
        Button *clearMemoryButton;
        Button *readMemoryButton;
        Button *setMemoryButton;
        Button *addToMemoryButton;
        Button *divisionButton;
        Button *timesButton;
        Button *minusButton;
        Button *plusButton;
        Button *squareRootButton;
        Button *powerButton;
        Button *reciprocalButton;
        Button *equalButton;
    };
    #endif