Functions

Functions are declared with def or function. Parameters require explicit types. The return type follows -> and defaults to None if omitted.

def add(Int a, Int b) -> Int:
    return a + b

def greet(String name):
    print("hello", name)

Parameters

Each parameter is written as Type name. Shared parameters use $Type or shared Type:

// or increment($Int counter)
def increment(shared Int counter):
    counter = counter + 1

Return type

def clamp(Int x, Int lo, Int hi) -> Int:
    if(x < lo): 
        return lo
    if(x > hi): 
        return hi
    return x

Lambdas

Anonymous functions are written with lam or lambda. A return type annotation is required when passing to methods like map.

let double = lambda(Int x) -> Int: x * 2

let nums = [1, 2, 3]
let tripled = nums.map(lambda(Int x) -> Int: x * 3)

A lambda body is a single expression. Lambdas capture the surrounding scope by reference.

First-class functions

Named functions and built-in converters can be passed directly without wrapping in a lambda:

let strings = ["1", "2", "3"]
let nums = strings.map(toInteger)