type
// Here are some examples of declaring set types.
// A variable of TMyMonth can take one and only one of
// one of its members.
TMyMonth = (Jan, Feb, Mar, Apr, May);
// TMyMonthSet can be an empty set (no months in it), or
// contain any combination of the above months.
TMyMonthSet = set of TMyMonth;
// TMySubMonthSet is a subset of the above set, only able
// to take on the first 3 months
TMySubMonthSet = set of Jan..Mar;
// TMyIntSet can be an empty set, or any combination of integers
// in the range of 1 to 15.
TMyIntSet = set of 1..15;
// TMySubIntSet can be an empty set, or any combination of integers
// in the range of 1 to 5.
TMySubIntSet = set of 1..5;
// Here are some examples of declaring set variables 
var
MyMonth: TMyMonth; // can only be one month (NOT a set)
MyMonthSet: TMyMonthSet; // can be more than one month
MyIntSet: TMyIntSet; // can be a combination of ints from 1 to 15 only
begin
// The TMyMonth type can only take on one value at a time
MyMonth := May;
// Sets can take on more than one value, and notice the use of square
// brackets
MyMonthSet := [Jan, Mar, May];
// MySubMonths can only take the values Jan..Mar. If you try to set it
// to May, you won't get a compile time error, but the set will be empty.
MyIntSet := [20]; // 20 is past the range for the set..so this should do nothing!
if MyIntSet = [] then
ShowMessage('MyIntSet is empty! (as expected...)');
// Here are some common operations you can do with sets:
// + Union operator
MyMonthSet := MyMonthSet + [Feb, Apr]; // Add 2 months to the set
// — Difference operator
MyMonthSet := MyMonthSet - [MyMonth]; // Remove May from the set
MyMonthSet := MyMonthSet - [Jan..Apr]; // Remove Jan through Apr
// The set should now be empty (use the equality operator = to test sets)
if MyMonthSet = [] then
ShowMessage('MyMonthSet is empty! (as expected...)');
// * Intersection operator
MyMonthSet := [Jan, Feb] * [Jan, Apr];
if MyMonthSet = [Jan] then
ShowMessage('MyMonthSet is Jan! (as expected...)');
// <= Subset operator
if [Jan, Apr] <= [Jan..Apr] then
ShowMessage('[Jan, Apr] <= [Jan..Apr], as expected...');
// <= Subset operator is the opposite of the above
// To test if an ordinal is in the set, us the "in" operator
if Jan in [Jan..Feb] then
ShowMessage('Jan in set [Jan..Feb]');
end.