- Qt 5.5
- Qt Widgets
- Calculator Example
- calculator.cpp Example File
- Qt 5.5.1 Reference Documentation

# calculator.cpp Example File

widgets/calculator/calculator.cpp

    /****************************************************************************
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    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
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    #include <QtWidgets>

    #include <cmath>

    #include "button.h"
    #include "calculator.h"

    Calculator::Calculator(QWidget *parent)
        : QWidget(parent)
    {
        sumInMemory = 0.0;
        sumSoFar = 0.0;
        factorSoFar = 0.0;
        waitingForOperand = true;

        display = new QLineEdit("0");
        display->setReadOnly(true);
        display->setAlignment(Qt::AlignRight);
        display->setMaxLength(15);

        QFont font = display->font();
        font.setPointSize(font.pointSize() + 8);
        display->setFont(font);

        for (int i = 0; i < NumDigitButtons; ++i) {
            digitButtons[i] = createButton(QString::number(i), SLOT(digitClicked()));
        }

        Button *pointButton = createButton(tr("."), SLOT(pointClicked()));
        Button *changeSignButton = createButton(tr("\302\261"), SLOT(changeSignClicked()));

        Button *backspaceButton = createButton(tr("Backspace"), SLOT(backspaceClicked()));
        Button *clearButton = createButton(tr("Clear"), SLOT(clear()));
        Button *clearAllButton = createButton(tr("Clear All"), SLOT(clearAll()));

        Button *clearMemoryButton = createButton(tr("MC"), SLOT(clearMemory()));
        Button *readMemoryButton = createButton(tr("MR"), SLOT(readMemory()));
        Button *setMemoryButton = createButton(tr("MS"), SLOT(setMemory()));
        Button *addToMemoryButton = createButton(tr("M+"), SLOT(addToMemory()));

        Button *divisionButton = createButton(tr("\303\267"), SLOT(multiplicativeOperatorClicked()));
        Button *timesButton = createButton(tr("\303\227"), SLOT(multiplicativeOperatorClicked()));
        Button *minusButton = createButton(tr("-"), SLOT(additiveOperatorClicked()));
        Button *plusButton = createButton(tr("+"), SLOT(additiveOperatorClicked()));

        Button *squareRootButton = createButton(tr("Sqrt"), SLOT(unaryOperatorClicked()));
        Button *powerButton = createButton(tr("x\302\262"), SLOT(unaryOperatorClicked()));
        Button *reciprocalButton = createButton(tr("1/x"), SLOT(unaryOperatorClicked()));
        Button *equalButton = createButton(tr("="), SLOT(equalClicked()));

        QGridLayout *mainLayout = new QGridLayout;
        mainLayout->setSizeConstraint(QLayout::SetFixedSize);
        mainLayout->addWidget(display, 0, 0, 1, 6);
        mainLayout->addWidget(backspaceButton, 1, 0, 1, 2);
        mainLayout->addWidget(clearButton, 1, 2, 1, 2);
        mainLayout->addWidget(clearAllButton, 1, 4, 1, 2);

        mainLayout->addWidget(clearMemoryButton, 2, 0);
        mainLayout->addWidget(readMemoryButton, 3, 0);
        mainLayout->addWidget(setMemoryButton, 4, 0);
        mainLayout->addWidget(addToMemoryButton, 5, 0);

        for (int i = 1; i < NumDigitButtons; ++i) {
            int row = ((9 - i) / 3) + 2;
            int column = ((i - 1) % 3) + 1;
            mainLayout->addWidget(digitButtons[i], row, column);
        }

        mainLayout->addWidget(digitButtons[0], 5, 1);
        mainLayout->addWidget(pointButton, 5, 2);
        mainLayout->addWidget(changeSignButton, 5, 3);

        mainLayout->addWidget(divisionButton, 2, 4);
        mainLayout->addWidget(timesButton, 3, 4);
        mainLayout->addWidget(minusButton, 4, 4);
        mainLayout->addWidget(plusButton, 5, 4);

        mainLayout->addWidget(squareRootButton, 2, 5);
        mainLayout->addWidget(powerButton, 3, 5);
        mainLayout->addWidget(reciprocalButton, 4, 5);
        mainLayout->addWidget(equalButton, 5, 5);
        setLayout(mainLayout);

        setWindowTitle(tr("Calculator"));
    }

    void Calculator::digitClicked()
    {
        Button *clickedButton = qobject_cast<Button *>(sender());
        int digitValue = clickedButton->text().toInt();
        if (display->text() == "0" && digitValue == 0.0)
            return;

        if (waitingForOperand) {
            display->clear();
            waitingForOperand = false;
        }
        display->setText(display->text() + QString::number(digitValue));
    }

    void Calculator::unaryOperatorClicked()
    {
        Button *clickedButton = qobject_cast<Button *>(sender());
        QString clickedOperator = clickedButton->text();
        double operand = display->text().toDouble();
        double result = 0.0;

        if (clickedOperator == tr("Sqrt")) {
            if (operand < 0.0) {
                abortOperation();
                return;
            }
            result = std::sqrt(operand);
        } else if (clickedOperator == tr("x\302\262")) {
            result = std::pow(operand, 2.0);
        } else if (clickedOperator == tr("1/x")) {
            if (operand == 0.0) {
                abortOperation();
                return;
            }
            result = 1.0 / operand;
        }
        display->setText(QString::number(result));
        waitingForOperand = true;
    }

    void Calculator::additiveOperatorClicked()
    {
        Button *clickedButton = qobject_cast<Button *>(sender());
        QString clickedOperator = clickedButton->text();
        double operand = display->text().toDouble();

        if (!pendingMultiplicativeOperator.isEmpty()) {
            if (!calculate(operand, pendingMultiplicativeOperator)) {
                abortOperation();
                return;
            }
            display->setText(QString::number(factorSoFar));
            operand = factorSoFar;
            factorSoFar = 0.0;
            pendingMultiplicativeOperator.clear();
        }

        if (!pendingAdditiveOperator.isEmpty()) {
            if (!calculate(operand, pendingAdditiveOperator)) {
                abortOperation();
                return;
            }
            display->setText(QString::number(sumSoFar));
        } else {
            sumSoFar = operand;
        }

        pendingAdditiveOperator = clickedOperator;
        waitingForOperand = true;
    }

    void Calculator::multiplicativeOperatorClicked()
    {
        Button *clickedButton = qobject_cast<Button *>(sender());
        QString clickedOperator = clickedButton->text();
        double operand = display->text().toDouble();

        if (!pendingMultiplicativeOperator.isEmpty()) {
            if (!calculate(operand, pendingMultiplicativeOperator)) {
                abortOperation();
                return;
            }
            display->setText(QString::number(factorSoFar));
        } else {
            factorSoFar = operand;
        }

        pendingMultiplicativeOperator = clickedOperator;
        waitingForOperand = true;
    }

    void Calculator::equalClicked()
    {
        double operand = display->text().toDouble();

        if (!pendingMultiplicativeOperator.isEmpty()) {
            if (!calculate(operand, pendingMultiplicativeOperator)) {
                abortOperation();
                return;
            }
            operand = factorSoFar;
            factorSoFar = 0.0;
            pendingMultiplicativeOperator.clear();
        }
        if (!pendingAdditiveOperator.isEmpty()) {
            if (!calculate(operand, pendingAdditiveOperator)) {
                abortOperation();
                return;
            }
            pendingAdditiveOperator.clear();
        } else {
            sumSoFar = operand;
        }

        display->setText(QString::number(sumSoFar));
        sumSoFar = 0.0;
        waitingForOperand = true;
    }

    void Calculator::pointClicked()
    {
        if (waitingForOperand)
            display->setText("0");
        if (!display->text().contains("."))
            display->setText(display->text() + tr("."));
        waitingForOperand = false;
    }

    void Calculator::changeSignClicked()
    {
        QString text = display->text();
        double value = text.toDouble();

        if (value > 0.0) {
            text.prepend(tr("-"));
        } else if (value < 0.0) {
            text.remove(0, 1);
        }
        display->setText(text);
    }

    void Calculator::backspaceClicked()
    {
        if (waitingForOperand)
            return;

        QString text = display->text();
        text.chop(1);
        if (text.isEmpty()) {
            text = "0";
            waitingForOperand = true;
        }
        display->setText(text);
    }

    void Calculator::clear()
    {
        if (waitingForOperand)
            return;

        display->setText("0");
        waitingForOperand = true;
    }

    void Calculator::clearAll()
    {
        sumSoFar = 0.0;
        factorSoFar = 0.0;
        pendingAdditiveOperator.clear();
        pendingMultiplicativeOperator.clear();
        display->setText("0");
        waitingForOperand = true;
    }

    void Calculator::clearMemory()
    {
        sumInMemory = 0.0;
    }

    void Calculator::readMemory()
    {
        display->setText(QString::number(sumInMemory));
        waitingForOperand = true;
    }

    void Calculator::setMemory()
    {
        equalClicked();
        sumInMemory = display->text().toDouble();
    }

    void Calculator::addToMemory()
    {
        equalClicked();
        sumInMemory += display->text().toDouble();
    }
    Button *Calculator::createButton(const QString &text, const char *member)
    {
        Button *button = new Button(text);
        connect(button, SIGNAL(clicked()), this, member);
        return button;
    }

    void Calculator::abortOperation()
    {
        clearAll();
        display->setText(tr("####"));
    }

    bool Calculator::calculate(double rightOperand, const QString &pendingOperator)
    {
        if (pendingOperator == tr("+")) {
            sumSoFar += rightOperand;
        } else if (pendingOperator == tr("-")) {
            sumSoFar -= rightOperand;
        } else if (pendingOperator == tr("\303\227")) {
            factorSoFar *= rightOperand;
        } else if (pendingOperator == tr("\303\267")) {
            if (rightOperand == 0.0)
                return false;
            factorSoFar /= rightOperand;
        }
        return true;
    }