Question

I’m not looking for any specific code examples, but could someone explain why I can’t get the ‘-1’ to function at the end of this switch statement? It keeps saying that there are “too many literals” for type char. (something close to that). Would I have to convert this to another type?

Thanks for any help, and please, just explain without giving code. I would love to learn this by hands on experiance 😀

Convert 7 char passed from ProcessInput() by reference to upper case
Use switch statement to translate char into their corresponding digits (case statement for each digit and each valid uppercase letter)
**TROUBLES WITH THIS PART***Write default case that returns error code (-1) for invalid letters
If no invalide letters, return 0

    static void ToDigit(ref char digit)
    {

        digit = Char.ToUpper(digit);
        char result;

        switch (digit)
        {
            case '0':  result = '0';
                break;

            case '1': result = '1';
                break;

            case '2':
            case 'A':
            case 'B':
            case 'C': result = '2';
                break;

            case '3':
            case 'D':
            case 'E':
            case 'F': result = '3';
                break;

            case '4':
            case 'G':
            case 'H':
            case 'I': result = '4';
                break;

            case '5':
            case 'J':
            case 'K':
            case 'L': result = '5';
                break;

            case '6':
            case 'M':
            case 'N':
            case 'O': result = '6';
                break;

            case '7':
            case 'P':
            case 'Q':
            case 'R':
            case 'S': result = '7';
                break;

            case '8':
            case 'T':
            case 'U':
            case 'V': result = '8';
                break;

            case '9':
            case 'W':
            case 'X':
            case 'Y':
            case 'Z': result = '9';
                break;
                //Says I can't enter -1 as char "too many characters in character literal
            default: result = 'e';
                break;
        }
        digit = result;
    }

Answer 1

A char is, as the name implies, a single character. A group of characters all “strung together” is called a string in C#.

If you want the integer value -1 as a char then you can do that by saying unchecked((char)(-1)) (*) but you should be aware that this is a very bad idea. I assume that this is your assignment:

Write default case that returns error code (-1) for invalid letters.

That’s not how things work in C#; returning a “bad” value to indicate failure is a “worst practice” — it is characteristic of 1970’s style C programming, but not C#.

The right thing to do here is to either (1) have no error cases at all; if there is no upper case form then just don’t transform the character at all, or (2) throw an exception if the input is bad, or (3) return a nullable char, and return null for the “bad” value.

Also, the fact that your program takes a ref rather than returning a value is deeply suspicious. A ToDigit method should be computing and returning result not mutating a variable.

I think whatever course of study you are taking was written decades ago, originally targetted a different language entirely, and was never updated to use modern best practices. I would seriously question the value of such materials.

---

Always say (T)(-1) in C# when casting the constant -1 to the type T, rather than (T)-1. If you write it the latter way, the reader can get confused about whether you mean “subtract one from T” or “cast negative one to type T”.