Ternary Operator

DWScript supports an expression-based if syntax, often called the ternary operator in other languages. It allows you to select a value based on a condition within a single expression.

Basic Syntax

The full syntax is if condition then expression1 else expression2.

var count := 10;
var status := if count > 0 then 'Active' else 'Empty';
PrintLn(status);

Active

Unlike the if statement, the ternary if is an expression that returns a value. Both branches must return compatible types.

Omitted Else (Default Values)

If the else clause is omitted, the expression evaluates to the default value for the result type if the condition is false.

var score := -5;
// If score is not positive, returns 0 (default for Integer)
var positiveScore := if score > 0 then score; 

PrintLn(positiveScore);

0

Type Inference & Classes

The ternary operator can infer types and even works with class types for polymorphic results.

type TBase = class end;
type TChild = class(TBase) end;

var cond := True;
// Result is TBase, even though one branch is TChild
var obj := if cond then TBase.Create else TChild.Create;

PrintLn(obj.ClassName);

TBase

Chaining & Nesting

Ternary expressions can be nested to handle multiple conditions.

var val := 2;
var description := if val = 1 then 'One' 
                   else if val = 2 then 'Two' 
                   else 'Many';

PrintLn(description);

Two

Practical Examples

In Function Parameters

Pass conditional values directly to functions without temporary variables.

procedure Log(msg: String);
begin
  PrintLn('LOG: ' + msg);
end;

var priority := True;
Log(if priority then 'URGENT' else 'Normal');

LOG: URGENT

With Collections

The ternary operator can return arrays or sets. Note that for arrays, you often need an explicit type to assist inference.

var selection: array of String := if True then ['A', 'B'] else ['C'];
PrintLn(selection.Length);

2