Enumerated Types & Sets

DWScript provides robust support for enumerations and sets, which are core features for writing clear and type-safe Pascal code.

Enumerated Types

An enumeration defines a set of named constants. DWScript supports three distinct styles of enumerations.

1. Classic Enumerations

Symbols are globally scoped within the unit. This is the traditional Pascal style.

type TDirection = (North, East, South, West);

// Type inference
var d1 := North;

// Explicit typing
var d2 : TDirection := North;

2. Scoped Enumerations

Using the enum keyword requires you to prefix the values with the type name. This prevents name collisions.

type TStatus = enum (Ready, Busy, Error);

// Type inference
var s1 := TStatus.Ready;

// Explicit typing
var s2 : TStatus := TStatus.Ready;

3. Flags (Bitmasks)

Using the flags keyword automatically assigns power-of-two values (1, 2, 4, 8...). These are designed to be used with bitwise or to combine multiple values.

type TFileAccess = flags (Read, Write, Execute); // 1, 2, 4

// Type inference
var access1 := TFileAccess.Read or TFileAccess.Write;

// Explicit typing
var access2 : TFileAccess := TFileAccess.Read or TFileAccess.Execute;

Sets

Sets are collections of values from an ordinal type (usually an enumeration). A set can hold any combination of its base type's values, or be empty.

A set of TEnum is stored efficiently as a bitfield. You can even cast a set to an Integer to see its underlying bitmask.

type TCards = (Club, Diamond, Heart, Spade);
type THand = set of TCards;

var hand: THand := [Club, Heart];

if Club in hand then
  PrintLn('You have a Club');

// Using ranges in sets
var allMinors: THand := [Club..Diamond];
if Heart in [Club..Spade] then
  PrintLn('Hearts are in the range');

hand.Include(Spade);
hand.Exclude(Club);

if hand = [] then
  PrintLn('Empty hand');
Result
You have a Club
Hearts are in the range

Built-in Methods

Enumerations and sets provide several built-in methods for convenience:

  • Enums:
    • TMyEnum.Low and TMyEnum.High return the first and last values.
    • TMyEnum.ByName('name') returns the value matching the string.
    • val.Name returns the name of the enumeration value as a string.
// Enum ByName
type TDirection = (North, East, South, West);
var dir := TDirection.ByName('South');
PrintLn(dir.Name);

// Set to Integer Cast
type TCards = (Club, Diamond, Heart, Spade);
type THand = set of TCards;
var mySet : THand := [Club, Spade]; // 0th and 3rd bits
PrintLn(Integer(mySet));
Result
South
9
  • Sets:
    • mySet.Include(Value) adds a value to the set.
    • mySet.Exclude(Value) removes a value from the set.
    • mySet.Contains(Value) is equivalent to the in operator.
← Strings Variants →
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