Question

For my book class I’m storing an ISBN number and I need to validate the data entered so I decided to use enumeration. (First three inputs must be single digits, last one must be a letter or digit.) However, I’m wondering if it is even possible to enumerate numbers. Ive tried putting them in as regular integers, string style with double quotes, and char style with single quotes.

Example:

class Book{
public:
   enum ISBN_begin{
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'
        };
   enum ISBN_last{
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', a, b, c, d, e, f, 
        g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z};

The compiler error says expected identifier which means that its seeing the numbers as values for the identifiers and not identifiers themselves. So is enumerating digits possible?

Answer 1

Why would you want to enumerate numbers? Enums exist to give numbers a name. If you want to store a number, store an integer – or in this case a char (as you also need characters to be stored). For validation, accept a string and write a function like this:

bool ISBN_Validate(string val)
{
    if (!val.length == <length of ISBN>) return false;
    if (val[0] < '0' || val[0] > '9') return false;
    foreach (char ch in val)
    {
        if (ch is not between '0' and 'z') return false;
    }
}

Easy – and no silly enumerations 😉