DelphiBasics
 InKeyword Used to test if a value is a member of a set
 Ordinal expression in Set expression
Description
The In keyword tests whether a value is in a set. It returns true if it is, false if not.
Notes
Sets are limited to 256 different values. Each element is equated with the Integer values 0,1,2 ... 255

Integer sets map directly to these element values, and are therefore limited to a high value of 255.

However, you may compare a value greater than 255 with an Integer set. Delphi simply uses the lowest byte of the Integer. For example, a test value of 258 would have a lower byte value of 3.
Related commands
 Exclude Exclude a value in a set variable Include Include a value in a set variable Set Defines a set of up to 255 distinct values

 Example code : Determine whether a character is a letter begin  IsLetter('G');  // G is a letter of the (uppercase) alphabet  IsLetter('1');  // 1 is not a letter end; // Test if a character is a letter procedure TForm1.IsLetter(Letter : char); var   Alphabet : set of 'A'..'Z'; begin   Alphabet := ['A'..'Z'];   if Letter In Alphabet then     ShowMessage(Letter+' is in the alphabet')   else     ShowMessage(Letter+' is NOT in the alphabet'); end; Show full unit code G is in the alphabet   1 is NOT in the alphabet