Kairo Functions: Free Functions, Methods, and Async

Kairo has one function keyword, func, and four ways to use it: free functions, instance methods, type functions, and async functions. Every signature is explicit. There is no overload resolution and no hidden receiver.

Free functions

A func declared at module scope is a free function.

public func calculateTotal(order: Order): Money {
    return order.total
}

Parameters are name: Type pairs separated by commas.
The return type follows the parameter list after a colon.
Omitting the return type means the function returns no value.

Instance methods

A func declared inside a value, object, or contract is an instance method.

public object Customer {
    public var name: Text

    public func rename(newName: Text) {
        this.name = newName
    }
}

Value methods have an immutable this receiver.
Object methods have an identity-bearing this and may mutate var members.
Contract methods are requirements: no body, just the signature.

Type functions

type func declares a function owned by the type itself, not by any instance. There is no this.

public value EmailAddress {
    value: Text

    public type func create(value: Text): EmailAddress {
        return EmailAddress {
            value: value
        }
    }
}

let email = EmailAddress.create("pete@example.com")

Use type func for named factories and type-scoped helpers. Kairo does not use static in v0.1.

Initialization

init runs once when an object is constructed. It cannot return a value and must assign every required immutable member before completing.

public object Customer {
    public id: CustomerId
    public var name: Text

    public init(id: CustomerId, name: Text) {
        this.id = id
        this.name = name
    }
}

Only objects have init. Values are assembled with a field block (see construction reference).

Async functions

Async functions declare that they may suspend. The async keyword is part of the signature so callers can see suspension might happen.

public async func fetchCustomer(id: CustomerId): Customer {
    return await CustomerApi.get(id)
}

await is only valid inside async func.
await waits for the awaited call; it does not unwrap Result.
Standalone task spawning and cancellation are deferred.

The async/await language shape is frozen for v0.1, but the async runtime is deferred. Design your APIs around async today; execution semantics land with the Pulse async runtime.

Return statements

return exits the current function, optionally with a value. The value must be assignment-compatible with the declared return type.

public func answer(): Int32 {
    return 42
}

public func log(message: Text) {
    Pulse.Console.out.writeLine(message)
    return
}

Calling functions

Positional arguments for free functions and instance methods.
Named arguments are required for object construction (see construction).
No default parameter values in v0.1.
No overload resolution: each function name is unique in its scope.

let total = calculateTotal(order)
customer.rename(newName: "Pete")
let email = EmailAddress.create("pete@example.com")

Next steps

Control flow

if, match, and how bindings interact with branching.

Functions reference

Complete spec-style reference for every callable form.

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Kairo Functions: Free Functions, Methods, and Async

Free functions

Instance methods

Type functions

Initialization

Async functions

Return statements

Calling functions

Next steps

Control flow

Functions reference

​Free functions

​Instance methods

​Type functions

​Initialization

​Async functions

​Return statements

​Calling functions

​Next steps

Control flow

Functions reference

Free functions

Instance methods

Type functions

Initialization

Async functions

Return statements

Calling functions

Next steps