<?pas
// Custom Class Operators Demo

// Example 1: Custom 'in' operator for range checking
type
  TDateRange = class
    StartDate, EndDate: Float;
    
    constructor Create(s, e: Float);
    begin
      StartDate := s;
      EndDate := e;
    end;
    
    function Contains(d: Float): Boolean;
    begin
      Result := (d >= StartDate) and (d <= EndDate);
    end;
    
    class operator in Float uses Contains;
  end;

var q1 := TDateRange.Create(
  EncodeDate(2024, 1, 1),
  EncodeDate(2024, 3, 31)
);

var testDate := EncodeDate(2024, 2, 15);
if testDate in q1 then
  PrintLn('Date is in Q1 2024');

// Example 2: Custom '+=' for fluent building
type
  TQueryBuilder = class
    FSql: String;
    
    procedure AddClause(clause: String);
    begin
      if FSql <> '' then FSql := FSql + ' ';
      FSql := FSql + clause;
    end;
    
    class operator += String uses AddClause;
  end;

var query := TQueryBuilder.Create;
query += 'SELECT *';
query += 'FROM users';
query += 'WHERE active = 1';
PrintLn('Query: ' + query.FSql);

// Example 3: Custom 'not in' automatically works
var otherDate := EncodeDate(2024, 5, 1);
if otherDate not in q1 then
  PrintLn('May 1st is NOT in Q1');
?>