OvumDocs

Syntax & Semantics (Description)

Functions

• Declared with fun, PascalCase names: fun Compute(a: Int): Int { ... }
• Pure functions: pure fun Hash(o: Object): Int { ... }
  • Side-effect free; VM may cache results.
  • If parameters include user-defined reference types, those types must implement IHashable.

Classes

• class Name implements IFace1, IFace2 { ... }

  • No class inheritance.
  • Access modifiers are mandatory on fields and methods.

  • Fields use val (immutable) or var (mutable):

    • private val Prefix: String
    • public var Count: Int

  • Methods must declare access and can be override/pure:

    • public override fun Run(): Int { ... }
  • Static fields supported; writing static var is unsafe.

  • Destructor: optional, overrides the implicit virtual destructor from Object.

    • Syntax: public destructor(): Void { ... } (no parameters, no return).
    • Called automatically by GC finalization; manual calls are unsafe.

Interfaces

• interface IGreeter { fun Greet(name: String): String; }

  • Methods are public and virtual by default.
  • No fields, no bodies.

Type Aliases

• Create type aliases for better readability: typealias UserId = Int
• Can be used anywhere a type is expected: fun ProcessUser(id: UserId): Void

Namespaces

• Namespace resolution with :: (e.g., sys::Print), declared with namespace keyword.

Preprocessor

• Preprocessor commands: #import, #define, #ifdef, #ifndef, #else, #undef.
• Multiple #define commands can be used to define the same symbol, as well as #undef to undefine a symbol.
• #import does not include the file at the location of the #import command. It adds a dependency for the current file, and after all dependencies are collected, they are included in the final compilation. Order is defined by the topological sort of the dependency graph and lexicographic order of the files to avoid cyclical dependencies and double inclusion.

Note: #define cannot be used to really define something, it is a way to control what code will be used.

Functional Objects (call)

• Classes or interfaces can declare a special call member that makes instances callable like functions.
• Classes define call, it may have other members.
• Interfaces contain undefined call member (maybe not one, with all interface rules applying).
• A function literal fun(...) : T { ... } can be coerced to a interface type that exposes a compatible call(...) : T (and only this).

Example:

interface CustomFunctional {
    call(a: Int?, b: Int?): Int
}

class DefinedFunctional {
    public var Multiplier: Int

    public fun DefinedFunctional(multiplier: Int): DefinedFunctional {
        this.Multiplier = multiplier
        return this
    }

    // Defines the callable behavior; pure body allowed
    public call(secondMultiplier: Int): Int = fun(secondMultiplier: Int): Int {
        return Multiplier * secondMultiplier
    }
}

val AddNullable: CustomFunctional = pure fun(a: Int?, b: Int?): Int {
    val aVal: int = a ?: 0  // Conversion from Int? to int
    val bVal: int = b ?: 0
    return aVal + bVal
}

fun Main(args: StringArray): Int {
    // Constructor call then functional call via `call`
    return AddNullable(2, DefinedFunctional(-1)(2))  // Implicit conversion from literals
}

This site is open source. Improve this page.