Gui Class Reference

Main window class for the calculator GUI. More...

#include <gui.h>

Inheritance diagram for Gui:

Collaboration diagram for Gui:

Public Member Functions
	Gui (QWidget *parent=nullptr)
	Constructs the GUI and initializes components.
	~Gui ()
	Destructor. Frees allocated resources.

Private Slots
void	on_btn_0_clicked ()
	Digit button handlers.
void	on_btn_1_clicked ()
void	on_btn_2_clicked ()
void	on_btn_3_clicked ()
void	on_btn_4_clicked ()
void	on_btn_5_clicked ()
void	on_btn_6_clicked ()
void	on_btn_7_clicked ()
void	on_btn_8_clicked ()
void	on_btn_9_clicked ()
void	on_btn_plus_clicked ()
	Operation button handlers.
void	on_btn_minus_clicked ()
void	on_btn_mul_clicked ()
void	on_btn_div_clicked ()
void	on_btn_mod_clicked ()
void	on_btn_pow_clicked ()
void	on_btn_root_clicked ()
	Appends square root operator.
void	on_btn_fac_clicked ()
	Appends factorial operator.
void	on_btn_clear_clicked ()
	Control buttons.
void	on_btn_equal_clicked ()
	Evaluates the current expression.
void	on_btn_dot_clicked ()
	Appends a decimal point to the current expression.

Private Member Functions
void	updateDisplay ()
	Updates the calculator display.
void	showError (mathlib::MathError err)
	Displays an error message based on mathlib error code.
void	keyPressEvent (QKeyEvent *event) override
	Keyboard input handler.
bool	endsWithOperator () const
	Helpers for input validation.
bool	hasOperator () const
	Checks if the expression already contains a binary operator.
int	findOperatorPos (QChar op) const
	Finds the position of the binary operator in the expression.
void	appendDigit (const QString &digit)
	Appends a digit to the expression.
void	appendOperator (const QString &op)
	Appends a binary operator to the expression.

Private Attributes
Ui::Gui *	ui
QString	currentExpression
bool	justEvaluated

Detailed Description

Main window class for the calculator GUI.

Handles user input, updates the display, and evaluates expressions using functions from mathlib.

Definition at line 25 of file gui.h.

Constructor & Destructor Documentation

Gui()

Gui::Gui ( QWidget * parent = nullptr )

explicit

Constructs the GUI and initializes components.

Parameters

parent

Pointer to parent widget.

Definition at line 18 of file gui.cpp.

    : QMainWindow(parent),
      ui(new Ui::Gui),
      justEvaluated(false)
{
    ui->setupUi(this);
    currentExpression.clear();
}

~Gui()

Gui::~Gui

(

)

Destructor. Frees allocated resources.

Definition at line 30 of file gui.cpp.

{
    delete ui;
}

Member Function Documentation

appendDigit()

void Gui::appendDigit ( const QString & digit )

private

Appends a digit to the expression.

If the calculator just finished an evaluation, the digit starts a new expression instead of appending to the old result.

Definition at line 108 of file gui.cpp.

{
    if (justEvaluated) {
        currentExpression.clear();
        justEvaluated = false;
    }
    currentExpression += digit;
    updateDisplay();
}

appendOperator()

void Gui::appendOperator ( const QString & op )

private

Appends a binary operator to the expression.

Prevents duplicate operators and enforces single-operation limit. If the user just evaluated, the result is kept and the operator is chained onto it.

Definition at line 125 of file gui.cpp.

{
    // After evaluation, chain onto the result
    if (justEvaluated) {
        justEvaluated = false;
    }
 
    // Don't allow an operator on an empty expression
    // (except minus, which creates a negative number)
    if (currentExpression.isEmpty()) {
        if (op == "-") {
            currentExpression += op;
            updateDisplay();
        }
        return;
    }
 
    // If expression already ends with an operator, replace it
    if (endsWithOperator()) {
        currentExpression.chop(1);
        currentExpression += op;
        updateDisplay();
        return;
    }
 
    // Only allow one binary operator per expression
    if (hasOperator()) {
        return;
    }
 
    currentExpression += op;
    updateDisplay();
}

endsWithOperator()

bool Gui::endsWithOperator ( ) const

private

Helpers for input validation.

Checks if the last character in the expression is an operator.

Returns

true if expression ends with an operator.

Definition at line 73 of file gui.cpp.

{
    if (currentExpression.isEmpty()) return false;
    QChar last = currentExpression.back();
    return last == '+' || last == '-' || last == '*' ||
           last == '/' || last == '%' || last == '^';
}

findOperatorPos()

int Gui::findOperatorPos ( QChar op ) const

private

Finds the position of the binary operator in the expression.

Skips a leading minus sign so that negative first operands are handled correctly (e.g. "-5+3" splits into -5 and 3).

Parameters

op	The operator character to find.

Returns

The index of the operator, or -1 if not found.

Definition at line 278 of file gui.cpp.

{
    // Start at 1 to skip a possible leading negative sign
    for (int i = 1; i < currentExpression.size(); ++i) {
        if (currentExpression[i] == op)
            return i;
    }
    return -1;
}

hasOperator()

bool Gui::hasOperator ( ) const

private

Checks if the expression already contains a binary operator.

Skips a leading minus sign (negative number) and looks for any binary operator in the remaining characters.

Returns

true if a binary operator is present.

Definition at line 88 of file gui.cpp.

{
    // Start scanning from index 1 to allow a leading negative sign
    for (int i = 1; i < currentExpression.size(); ++i) {
        QChar c = currentExpression[i];
        if (c == '+' || c == '*' || c == '/' || c == '%' || c == '^')
            return true;
        // A '-' that isn't at position 0 counts as an operator
        if (c == '-')
            return true;
    }
    return false;
}

keyPressEvent()

void Gui::keyPressEvent ( QKeyEvent * event )

overrideprivate

Keyboard input handler.

Handles keyboard input for the calculator.

Maps keyboard keys to their corresponding button actions.

Parameters

event

The key press event.

Definition at line 384 of file gui.cpp.

{
    int key = event->key();
 
    // Digit keys 0-9
    if (key >= Qt::Key_0 && key <= Qt::Key_9) {
        appendDigit(QString::number(key - Qt::Key_0));
        return;
    }
 
    switch (key) {
        // Basic operators
        case Qt::Key_Plus:
            appendOperator("+");
            break;
        case Qt::Key_Minus:
            appendOperator("-");
            break;
        case Qt::Key_Asterisk:
            appendOperator("*");
            break;
        case Qt::Key_Slash:
            appendOperator("/");
            break;
        case Qt::Key_Percent:
            appendOperator("%");
            break;
        case Qt::Key_AsciiCircum:
            appendOperator("^");
            break;
        case Qt::Key_Exclam:
            on_btn_fac_clicked();
            break;
 
        // Decimal point
        case Qt::Key_Period:
        case Qt::Key_Comma:
            on_btn_dot_clicked();
            break;
 
        // Evaluate
        case Qt::Key_Return:
        case Qt::Key_Enter:
        case Qt::Key_Equal:
            on_btn_equal_clicked();
            break;
 
        // Backspace — delete last character
        case Qt::Key_Backspace:
            if (justEvaluated) {
                currentExpression.clear();
                justEvaluated = false;
            } else if (!currentExpression.isEmpty()) {
                currentExpression.chop(1);
            }
            updateDisplay();
            break;
 
        // Clear
        case Qt::Key_Escape:
        case Qt::Key_Delete:
        case Qt::Key_C:
            on_btn_clear_clicked();
            break;
 
        default:
            QMainWindow::keyPressEvent(event);
            break;
    }
}

on_btn_0_clicked

void Gui::on_btn_0_clicked ( )

privateslot

Digit button handlers.

Definition at line 161 of file gui.cpp.

{ appendDigit("0"); }

on_btn_1_clicked

void Gui::on_btn_1_clicked ( )

privateslot

Definition at line 162 of file gui.cpp.

{ appendDigit("1"); }

on_btn_2_clicked

void Gui::on_btn_2_clicked ( )

privateslot

Definition at line 163 of file gui.cpp.

{ appendDigit("2"); }

on_btn_3_clicked

void Gui::on_btn_3_clicked ( )

privateslot

Definition at line 164 of file gui.cpp.

{ appendDigit("3"); }

on_btn_4_clicked

void Gui::on_btn_4_clicked ( )

privateslot

Definition at line 165 of file gui.cpp.

{ appendDigit("4"); }

on_btn_5_clicked

void Gui::on_btn_5_clicked ( )

privateslot

Definition at line 166 of file gui.cpp.

{ appendDigit("5"); }

on_btn_6_clicked

void Gui::on_btn_6_clicked ( )

privateslot

Definition at line 167 of file gui.cpp.

{ appendDigit("6"); }

on_btn_7_clicked

void Gui::on_btn_7_clicked ( )

privateslot

Definition at line 168 of file gui.cpp.

{ appendDigit("7"); }

on_btn_8_clicked

void Gui::on_btn_8_clicked ( )

privateslot

Definition at line 169 of file gui.cpp.

{ appendDigit("8"); }

on_btn_9_clicked

void Gui::on_btn_9_clicked ( )

privateslot

Definition at line 170 of file gui.cpp.

{ appendDigit("9"); }

on_btn_clear_clicked

void Gui::on_btn_clear_clicked ( )

privateslot

Control buttons.

Clears the current expression and resets display.

Definition at line 263 of file gui.cpp.

{
    currentExpression.clear();
    justEvaluated = false;
    updateDisplay();
}

on_btn_div_clicked

void Gui::on_btn_div_clicked ( )

privateslot

Definition at line 177 of file gui.cpp.

{ appendOperator("/"); }

on_btn_dot_clicked

void Gui::on_btn_dot_clicked ( )

privateslot

Appends a decimal point to the current expression.

Only allows one decimal point per number segment. If the calculator just evaluated, clears the expression first.

Definition at line 187 of file gui.cpp.

{
    if (justEvaluated) {
        currentExpression.clear();
        justEvaluated = false;
    }
 
    // Find the current number segment (after the last operator)
    int lastOp = -1;
    for (int i = currentExpression.size() - 1; i >= 0; --i) {
        QChar c = currentExpression[i];
        if (c == '+' || c == '-' || c == '*' ||
            c == '/' || c == '%' || c == '^') {
            lastOp = i;
            break;
        }
    }
    QString segment = currentExpression.mid(lastOp + 1);
 
    // Only add a dot if this number segment doesn't already have one
    if (!segment.contains('.')) {
        currentExpression += ".";
        updateDisplay();
    }
}

on_btn_equal_clicked

void Gui::on_btn_equal_clicked ( )

privateslot

Evaluates the current expression.

Supports basic binary operations and simple unary operations. Displays error messages if invalid operations occur.

Definition at line 294 of file gui.cpp.

{
    if (currentExpression.isEmpty())
        return;
 
 
    if (justEvaluated)
        return;
 
 
    if (endsWithOperator())
        return;
 
    mathlib::MathError err = mathlib::OK;
    double result = 0.0;
    bool evaluated = false;
 
 
 
 
    if (currentExpression.endsWith("!")) {
        int val = currentExpression.chopped(1).toInt();
        result = mathlib::factorial(val, err);
        evaluated = true;
    }
 
    else if (currentExpression.startsWith("√")) {
        double val = currentExpression.mid(1).toDouble();
        result = mathlib::root(val, 2, err);
        evaluated = true;
    }
 
 
 
    if (!evaluated) {
        int pos = -1;
        QChar op = '\0';
 
 
        const QString ops = "+*/%^";
        for (QChar c : ops) {
            pos = findOperatorPos(c);
            if (pos != -1) { op = c; break; }
        }
 
        if (pos == -1) {
            pos = findOperatorPos('-');
            if (pos != -1) op = '-';
        }
 
        if (pos != -1) {
            double left  = currentExpression.left(pos).toDouble();
            double right = currentExpression.mid(pos + 1).toDouble();
 
            if (op == '+')      result = mathlib::add(left, right);
            else if (op == '-') result = mathlib::subtract(left, right);
            else if (op == '*') result = mathlib::multiply(left, right);
            else if (op == '/') result = mathlib::divide(left, right, err);
            else if (op == '%') result = mathlib::modulo(left, right, err);
            else if (op == '^') result = mathlib::power(left, static_cast<int>(right));
 
            evaluated = true;
        }
    }
 
    // Plain number — just keep it
    if (!evaluated) {
        result = currentExpression.toDouble();
    }
 
    if (err != mathlib::OK) {
        showError(err);
        currentExpression.clear();
        justEvaluated = false;
        updateDisplay();
        return;
    }
 
    currentExpression = QString::number(result);
    justEvaluated = true;
    updateDisplay();
}

on_btn_fac_clicked

void Gui::on_btn_fac_clicked ( )

privateslot

Appends factorial operator.

Only allowed at the end of a number (unary postfix operator). Prevents factorial on an empty expression or after an operator.

Definition at line 238 of file gui.cpp.

{
    if (justEvaluated) {
        justEvaluated = false;
    }
 
    if (currentExpression.isEmpty() || endsWithOperator())
        return;
 
    // Don't allow factorial if there's already an operator (keeps single-op rule)
    // but do allow it as the sole operation on a plain number
    if (hasOperator())
        return;
 
    // Don't allow double factorial
    if (currentExpression.endsWith("!"))
        return;
 
    currentExpression += "!";
    updateDisplay();
}

on_btn_minus_clicked

void Gui::on_btn_minus_clicked ( )

privateslot

Definition at line 175 of file gui.cpp.

{ appendOperator("-"); }

on_btn_mod_clicked

void Gui::on_btn_mod_clicked ( )

privateslot

Definition at line 178 of file gui.cpp.

{ appendOperator("%"); }

on_btn_mul_clicked

void Gui::on_btn_mul_clicked ( )

privateslot

Definition at line 176 of file gui.cpp.

{ appendOperator("*"); }

on_btn_plus_clicked

void Gui::on_btn_plus_clicked ( )

privateslot

Operation button handlers.

Definition at line 174 of file gui.cpp.

{ appendOperator("+"); }

on_btn_pow_clicked

void Gui::on_btn_pow_clicked ( )

privateslot

Definition at line 179 of file gui.cpp.

{ appendOperator("^"); }

on_btn_root_clicked

void Gui::on_btn_root_clicked ( )

privateslot

Appends square root operator.

Only allowed at the start of an expression (unary prefix operator).

Definition at line 218 of file gui.cpp.

{
    if (justEvaluated) {
        currentExpression.clear();
        justEvaluated = false;
    }
 
    // √ is a prefix unary op — only valid at the beginning
    if (currentExpression.isEmpty()) {
        currentExpression = "√";
        updateDisplay();
    }
}

showError()

void Gui::showError ( mathlib::MathError err )

private

Displays an error message based on mathlib error code.

Parameters

err	Error type returned from mathlib.

Definition at line 39 of file gui.cpp.

{
    switch (err) {
        case mathlib::DIVISION_BY_ZERO:
            QMessageBox::warning(this, "Error", "Division by zero!");
            break;
        case mathlib::NEGATIVE_FACTORIAL:
            QMessageBox::warning(this, "Error", "Factorial of negative number!");
            break;
        case mathlib::INVALID_ROOT:
            QMessageBox::warning(this, "Error", "Invalid root operation!");
            break;
        case mathlib::INVALID_ARGUMENT:
            QMessageBox::warning(this, "Error", "Invalid argument!");
            break;
        default:
            break;
    }
}

updateDisplay()

void Gui::updateDisplay ( )

private

Updates the calculator display.

If the expression is empty, displays 0.

Definition at line 64 of file gui.cpp.

{
    ui->display->setText(currentExpression.isEmpty() ? "0" : currentExpression);
}

Member Data Documentation

currentExpression

QString Gui::currentExpression

private

Definition at line 63 of file gui.h.

justEvaluated

bool Gui::justEvaluated

private

Definition at line 64 of file gui.h.

ui

Ui::Gui* Gui::ui

private

Definition at line 62 of file gui.h.

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The documentation for this class was generated from the following files:

• gui/gui.h
• gui/gui.cpp