private: System::Void ButtonCalculate_Click(System::Object^  sender, System::EventArgs^  e) {
        //run the calculation
        {
            Token[] tokens = Tokenize(CalculateExpression);
        }

        //display result
    }

    private: Token Tokenize(String str)
    {
        string[] split = SplitForTokenize(str);
        List<Token> tokens = new List<Token>();
        foreach(string s in split)
        {
            Token t = Token.StringToToken(s);
            if (s == "-")
            {
                if (tokens.Count == 0 || tokens[tokens.Count - 1].GetTokenType == Token.TokenType.Left_Para || tokens[tokens.Count - 1].GetTokenType == Token.TokenType.Operator)
                {
                    t.SetValues('_', Token.Associativity.Right, 30, 1);
                }
            }
            tokens.Add(t);
        }
        return tokens.ToArray();
    }

    private: String SplitForTokenize(String str)
    {
        str = str.Replace("*", " * ");
        str = str.Replace("/", " / ");
        str = str.Replace("+", " + ");
        str = str.Replace("-", " - ");
        str = str.Replace("(", " ( ");
        str = str.Replace(")", " ) ");
        str = str.Trim();
        while (str.Contains("  ")
            str = str.Replace("  ", "");
        return str.Split(' ');
    }