Functions

Functions are defined with the keyword fun with the follwing syntax

fun <function_name> (<parameters>)
{
    // logic required

    return <expression>;
}

An example is:

fun add(a, b)
{
    var c = a + b;
    return c;
}

Closures

Lox functions support closures, thus the below program prints 10 appropriately.

fun outer()
{
    var x = 10;
    fun inner()
    {
        print x;
    }

    return inner;
}

var f = outer();

f();

Lox functions are first-class i.e they can be treated like any other varibale and be passed into functions, be returned by functions and be assigned to some variable. The above example showcases that too.

Lambdas / Anonymous Functions

Lox supports anonymous functions too. The syntax remains mostly the same with the exception of the function name not being included in the definition. These lambdas are considered expressions by lox.

Syntax

fun (<parameters>) {
    <statements>
}

Example

var fibonacci = fun (a){
    if (a == 0) return 0;
    if (a == 1 or a == 2) return 1;

    return fibonacci(a - 1) + fibonacci(a - 2);
};

print fibonacci(10);    

Warning

Using return outside a function or method throws an error.

Native functions

clock

Returns the time elapsed since the program started execution in seconds.