Delphi Basics : In command

DelphiBasics

In
Keyword

Used to test if a value is a member of a set

keyword In(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

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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