freepascal.compiler/docs/refex/ex111.pp

program Example111;

{ Program to demonstrate the Include/Exclude functions }

Type
  TEnumA = (aOne,aTwo,aThree);
  TEnumAs = Set of TEnumA;
  
Var
  SA : TEnumAs;

  Procedure PrintSet(S : TEnumAs);
  
  var 
    B : Boolean;
    
    procedure DoEl(A : TEnumA; Desc : String);
    
    begin
      If A in S then
        begin
        If B then 
          Write(',');
        B:=True;
        Write(Desc);
        end;
    end;
    
  begin
    Write('[');
    B:=False;
    DoEl(aOne,'aOne');
    DoEl(aTwo,'aTwo');
    DoEl(aThree,'aThree');
    Writeln(']')  
  end;

begin
  SA:=[];
  Include(SA,aOne);
  PrintSet(SA);
  Include(SA,aThree);
  PrintSet(SA);
  Exclude(SA,aOne);
  PrintSet(SA);
  Exclude(SA,aTwo);
  PrintSet(SA);
  Exclude(SA,aThree);
  PrintSet(SA);
end.