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Types

Arden is strongly and statically typed. Every variable must have a type known at compile time.

Primitive Types

Type Description Example
Integer 64-bit signed integer 42, -1
Float 64-bit floating point 3.14, -0.01
Boolean True or False true, false
Char Unicode character 'a', '🚀'
String UTF-8 encoded string "Hello"
None Unit type (empty value) None

Integers

Currently, Integer is the primary integer type.

x: Integer = 100_000; // Underscores can be used for readability

Floats

f: Float = 1.0;
sum: Float = 1 + 2.5;
same: Boolean = 1 == 1.0;
choice: Float = if (flag) { 1 } else { 2.5 };

Rules worth remembering:

  • Arden promotes Integer to Float inside mixed scalar numeric expressions.
  • Assignments still require a Float result on the right-hand side; there is no blanket implicit conversion step.
  • Wrapped/container types stay invariant, so Option<Integer> does not implicitly become Option<Float>, and Range<Integer> does not implicitly become Range<Float>.

Booleans

Used in conditional logic.

isValid: Boolean = true;
if (isValid) { ... }

Strings

Strings are heap-allocated and UTF-8 encoded.

s: String = "Text";

None

The None type represents the absence of a value, similar to void in C or () in Rust. It has a single value: None.

function doWork(): None {
    return None;
}

Reference Types

Arden allows references to values.

  • &T: Immutable reference.
  • &mut T: Mutable reference.

See Ownership and Borrowing for more details.

Composite Types

  • Lists: List<T> - See Collections
  • Maps: Map<K, V> - See Collections
  • User-defined: Classes, Enums, Interfaces.

Built-in Generic Constructors

Built-in generic constructor argument rules are checked at compile time:

  • List<T>() and List<T>(capacity: Integer) are valid.
  • List<T>(capacity) preallocates backing storage only; it does not create capacity elements or change length().
  • Map<K, V>(), Set<T>(), Option<T>(), and Result<T, E>() accept no value arguments.
  • Passing extra or incompatible constructor arguments is a type error.
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