Functions

Like many languages today, functions in Teascript are blocks of code that allow you to encapsulate code for reuse. Functions can be created using the function keyword followed by the function name, a set of parentheses for parameters, and a block of code enclosed in curly braces.

function greet()
{
    print("Hello world!")
}

To call the function, simply use its name followed by parentheses:

greet()     // Hello world!

Function parameters

Default parameters:

function greet(name = "Guest")
{
    console.log("Hello, " + name + "!");
}

greet()         // Hello, Guest!
greet("Alice")  // Hello, Alice!

Rest parameters:

function sum(...numbers) 
{
    return numbers.reduce((total, num) => total + num, 0)
}

print(sum(1, 2, 3)) // 6
print(sum(4, 5))    // 9

Returning values

Functions can return values using the return statement. This allows the function to pass a value back to a caller.

function add(a, b)
{
    return a + b
}

var result = add(5, 3)
print(result)     // 8

If return isn’t used by the function, it will return nil:

function thing() { }
print(thing())  // nil

Closures

As one might expect, functions are closures. A closure is a function that can access variables defined outside of their scope. They will hold onto closed-over variables even after leaving the scope where the function is defined:

function make_counter()
{
    var count = 0
    return function() {
        count++
        return count
    }
}

var counter = make_counter()
print(counter())    // 1
print(counter())    // 2

Lambdas