Question

I am working on a Reverse polish notation calculator. I created a method that will take care of the calculations but there are three lines in my code that are causing an error. After every = an operation is performed and then displayed. I am trying to grab the string from TxtInputBox and convert to integers but it always shows the catch message Please check the input. Then nothing gets calculated or display. I am sure that my first if statement will check for actual integers and avoid the characters. My ultimate goal is to input a formula in rpn format and have the result display in the multiline textbox.

Sample Input 5 6 -=

Code

namespace rpncalc
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void RPNCalc(TextBox TxtBoxInputbox, TextBox TxtBoxOutputbox)
        {
            Stack<int> stackone = new Stack<int>();
            stackone.Clear();
            string[] inputarray = TxtBoxInputbox.Text.Split();
            int end = inputarray.Length - 1;
            int numinput;
            int i = 0;

            do
            {
                if(inputarray[i] != "=" && inputarray[i] != "+" && inputarray[i] != "-" && inputarray[i] != "*" && inputarray[i] != "/")  
                {
                    try
                    {
                        numinput = Convert.ToInt32(inputarray[i]);
                        stackone.Push(numinput);
                    }
                    catch
                    {
                        MessageBox.Show("Please check the input");
                    }
                }

                    else if (inputarray[i]== "+")
                    {
                        try
                        {
                            int store1 = stackone.Pop();
                            int store2 = stackone.Pop();
                            stackone.Push(store2 + store1);
                        }
                        catch
                        {
                        }
                    }

                    else if (inputarray[i]== "-")
                    {
                        try
                        {
                            int store1 = stackone.Pop();
                            int store2 = stackone.Pop();
                            stackone.Push(store2 + store1);
                        }
                        catch
                        {
                        }
                    }

                    else if (inputarray[i]== "+")
                    {
                        try
                        {
                            int store1 = stackone.Pop();
                            int store2 = stackone.Pop();
                            stackone.Push(store2 + store1);
                        }
                        catch
                        {
                        }
                    }

                    else if (inputarray[i]== "*")
                    {
                        try
                        {
                            int store1 = stackone.Pop();
                            int store2 = stackone.Pop();
                            stackone.Push(store2 + store1);
                        }
                        catch
                        {
                        }
                    }

                    else if (inputarray[i]== "/")
                    {
                        try
                        {
                            int store1 = stackone.Pop();
                            int store2 = stackone.Pop();
                            stackone.Push(store2 + store1);
                        }
                        catch
                        {
                        }
                    }

            }
            while(i < end && inputarray[i]!= "=" && stackone.Count != 0);
            string txtout = TxtInputBox + " " + stackone.Pop().ToString() + Environment.NewLine;
            TxtOutputBox.AppendText(txtout);
            TxtInputBox.Clear();

        }

        private void Btn_Calc_Click(object sender, EventArgs e)
        {
            RPNCalc(TxtInputBox, TxtOutputBox);
        }

    }
}

Answer 1

What are you doing to increment i after each iteration of your do loop? I tried out your code and it seems like i is never incremented. Also, when you catch and run

catch
{
    MessageBox.Show("Please check the input");
}

You could perhaps change it to:

catch (Exception e) 
{
    MessageBox.Show(e.ToString());
}

so you could be sure of just what you’re catching, and why.

Edit:

Here’s my version of your code, now working correctly:

• i is incremented in each iteration
• Fixed the typo in the minus, multiplication and division operators that made them do addition instead
• Removed the redundant addition operator

namespace rpncalc {
    public partial class Form1 : Form {
        public Form1 () {
            InitializeComponent();
        }

        private void RPNCalc (TextBox TxtBoxInputbox, TextBox TxtBoxOutputbox) {
            Stack<int> stackone = new Stack<int>();
            stackone.Clear();
            string[] inputarray = TxtBoxInputbox.Text.Split();
            int end = inputarray.Length - 1;
            int numinput;
            int i = 0;

            do {
                if (inputarray[i] != "=" && inputarray[i] != "+" && inputarray[i] != "-" && inputarray[i] != "*" && inputarray[i] != "/") {
                    try {
                        numinput = Convert.ToInt32(inputarray[i]);
                        stackone.Push(numinput);
                    } catch (Exception e) {
                        MessageBox.Show(e.ToString());
                    }
                } else if (inputarray[i] == "+") {
                    try {
                        int store1 = stackone.Pop();
                        int store2 = stackone.Pop();
                        stackone.Push(store2 + store1);
                    } catch {
                    }
                } else if (inputarray[i] == "-") {
                    try {
                        int store1 = stackone.Pop();
                        int store2 = stackone.Pop();
                        stackone.Push(store2 - store1);
                    } catch {
                    }
                } else if (inputarray[i] == "*") {
                    try {
                        int store1 = stackone.Pop();
                        int store2 = stackone.Pop();
                        stackone.Push(store2 * store1);
                    } catch {
                    }
                } else if (inputarray[i] == "/") {
                    try {
                        int store1 = stackone.Pop();
                        int store2 = stackone.Pop();
                        stackone.Push(store2 / store1);
                    } catch {
                    }
                }
            }
            while (i++ < end && inputarray[i] != "=" && stackone.Count != 0);
            string txtout = TxtInputBox.Text + " " + stackone.Pop().ToString() + Environment.NewLine;
            TxtOutputBox.AppendText(txtout);
            TxtInputBox.Clear();

        }

        private void Btn_Calc_Click (object sender, EventArgs e) {
            RPNCalc(TxtInputBox, TxtOutputBox);
        }
    }
}