Delphi: How to have non-contiguous subrange enumeration type?

Question

While the following subrange enumeration declaration works:

type
   TReceiptCode = 'A'..'F';

This does not:

type
   TReceiptCode = ' ','A'..'F', 'R';

Nor does

type
    TReceiptCode = ' ','A','B','C','D','E','F','R';

How can i declare a subrange type with non-contiguous values?

Answer 1

Unfortunately, I don't think there's any way to do that. You can declare a (new) non-contiguous enumeration, or a subrange of an existing type, but not both.

Answer 2

Could you use a set instead?

TSomeCharSet= Set of Char;

SomeChars: TSomeCharSet = [' ','A','B','C','D','E','F','R'];

Could be granny and egg situation but I'm not sure what you are using then for :) ...

Well all you are left with then is creating TNonContigousCharRange yourself using a Set or array as the limiting "Range" and raising an exception when it is out of range or having a SetReceiptCode procedure to do a similar thing.

Answer 3

To all previous answers I would add simply that the clue is in the name of the type: sub**range**

Simply put, a range has a lower and an upper bound. What you describe is a set (or a subset), not a subrange so of course you cannot express it as a subrange.