When I press a special button the following char sequence is set on the QLineEdit object:

add($,$)
Each $ character is a placeholder for an int, which I'm supposed to provide by clicking on the [0-9] buttons. Each click inserts a new digit until I press Enter. Then the cursor moves to the second placeholder, selects it and wait for my click. But there is a problem.

When add($,$) appears, I select the first placeholder and the program wait for the first digit which further substitutes the placeholder by itself. But when I finish entering the first number and move on to entering the second number each new digit doesn't erase the $ char, it just shifts it right. I tried almost everything I could imagine and it still doesn't work.

Can anyone help with an advice please? Here is the code:

void MainWindow::operation_clicked()
{
    QString operation((qobject_cast<QPushButton*>(sender()))->text());
    if(operation == "add($,$)")
    {
        ui->lineEdit->insert(operation);
        ui->lineEdit->cursorBackward(false, 3);
        ui->lineEdit->setSelection(ui->lineEdit->cursorPosition(),-1);
    }
}
```

```
void MainWindow::digit_clicked()
{
    if(expected_operands != 0 && printed_digits < MAXLEN)
    {
        QString num((qobject_cast<QPushButton*>(sender()))->text());
        ui->lineEdit->insert(num);
        ui->lineEdit->setFocus();
        ++printed_digits;
    }
}
``

```
void MainWindow::enter_pressed()
{
    if(expected_operands != 0)
    {
        ui->lineEdit->setSelection(ui->lineEdit->cursorPosition(), (-printed_digits-sign));
        current_argument = (QString(ui->lineEdit->selectedText())).toInt();
        --expected_operands;
        ui->lineEdit->deselect();
        if(expected_operands != 0)
        {
            ui->lineEdit->cursorForward(false, sign+printed_digits+2);
            ui->lineEdit->setSelection(ui->lineEdit->cursorPosition(),-1);
        }
        ui->lineEdit->setFocus();
        printed_digits = 0;
    }
}

````
Everything is realised using SIGNAL-SLOT mechanism.