Functions

Syntax

To declare a function, just use the keyword func.

func greet() {
    puts 'Hello'
}

Print it:

puts greet    // main@greet

Call it:

greet()    // Hello

// todo

Arrow functions

A simple arrow function:

var greet = () => {
    puts 'Hello'
}

You can print greet out:

puts greet
// fn@abcd3458

And call it:

greet()
// Hello

One return expression, no brackets

var add = (a, b) => a + b
puts add(4, 5)    // 9

More example:

var linear = (x) => x
var relu = (x) => x > 0 ? x : 0

func active(x, fn) {
    return fn(x)
}

puts active(10, linear)

The difference between two types of function is at usage.

• Normal function can only be declared in top-level of code.

• Arrow function can be declared everywhere.

In JavaScript, a single-param arrow function can be declared without parenthese. But here, this case is not supported.

Variadic function

A variadic function helps you to group multiple parameters to an array.

func va(...params) {
    puts params
}

va(1, 2, 'abc')    // [1, 2, 'abc']

You also can pass parameters into a function call.

func a(x, y) {
    return x + y
}

func b(x, y) {
    return a(...)
}

puts b(4, 5)    // 9

// todo

Notes

You cannot call a non-callable value.

null()
//  ^-- Attempt to call a null value.

A function name cannot be declared more than one time.

func abc() {}
func abc() { return 10 }
//   ^^^-- This variable has already been declared.

A function variable is immutable, so you cannot modify it.

func fn() {}
    fn = 100
//  ^^-- This variable is immutable.