calculator.cpp Example File

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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;
  }