Qt 5.11 | Qt Widgets | Calculator Example | calculator.cpp Example File

Qt 5.11.3 Reference Documentation

# calculator.cpp Example File

widgets/calculator/calculator.cpp

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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;
      }