Calculator.cpp

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// ======================================================================
//  Calculator.cpp
// ======================================================================
//                   This file is a part of the book 
//             "Qt 5.10 Professional programming with C++"
//                       http://qt-book.com
// ======================================================================
//  Copyright (c) 2017 by Max Schlee
// ======================================================================

#include <QtWidgets>
#include "Calculator.h"

// ----------------------------------------------------------------------
Calculator::Calculator(QWidget* pwgt/*= 0*/) : QWidget(pwgt)
{
    m_plcd = new QLCDNumber(12);
    m_plcd->setSegmentStyle(QLCDNumber::Flat);
    m_plcd->setMinimumSize(150, 50);

    QChar aButtons[4][4] = {{'7', '8', '9', '/'},
                            {'4', '5', '6', '*'},
                            {'1', '2', '3', '-'},
                            {'0', '.', '=', '+'}
                           };

    //Layout setup
    QGridLayout* ptopLayout = new QGridLayout;
    ptopLayout->addWidget(m_plcd, 0, 0, 1, 4);    
    ptopLayout->addWidget(createButton("CE"), 1, 3);

    for (int i = 0; i < 4; ++i) {
        for (int j = 0; j < 4; ++j) {
           ptopLayout->addWidget(createButton(aButtons[i][j]), i + 2, j);
        }
    }
    setLayout(ptopLayout);
}

// ----------------------------------------------------------------------
QPushButton* Calculator::createButton(const QString& str)
{
    QPushButton* pcmd = new QPushButton(str);
    pcmd->setMinimumSize(40, 40);
    connect(pcmd, SIGNAL(clicked()), SLOT(slotButtonClicked()));
    return pcmd;
}


// ----------------------------------------------------------------------
void Calculator::calculate()
{
    qreal   fOperand2    = m_stk.pop().toFloat();
    QString strOperation = m_stk.pop();
    qreal   fOperand1    = m_stk.pop().toFloat();
    qreal   fResult      = 0;

    if (strOperation == "+") {
        fResult = fOperand1 + fOperand2;
    }
    if (strOperation == "-") {
        fResult = fOperand1 - fOperand2;
    }
    if (strOperation == "/") {
        fResult = fOperand1 / fOperand2;
    }
    if (strOperation == "*") {
        fResult = fOperand1 * fOperand2;
    }
    m_plcd->display(fResult);
}

// ----------------------------------------------------------------------
void Calculator::slotButtonClicked()
{
    QString str = ((QPushButton*)sender())->text();

    if (str == "CE") {
        m_stk.clear();
        m_strDisplay = "";
        m_plcd->display("0");
        return;
    }
    if (str.contains(QRegExp("[0-9]"))) {
        m_strDisplay += str;
        m_plcd->display(m_strDisplay.toDouble());
    }
    else if (str == ".") {
        m_strDisplay += str;
        m_plcd->display(m_strDisplay);
    }
    else {
        if (m_stk.count() >= 2) {
            m_stk.push(QString().setNum(m_plcd->value()));
            calculate();
            m_stk.clear();
            m_stk.push(QString().setNum(m_plcd->value()));
            if (str != "=") {
                m_stk.push(str);
            }
        }
        else {
            m_stk.push(QString().setNum(m_plcd->value()));
            m_stk.push(str);
            m_strDisplay = "";
        }
    }
}