Syntax

Comments

// comments

Printing to Std Output

print "Hello, world!";

DATA TYPES

Booleans

true; // Not false.
false; // Not _not_ false

Numbers

1234; // An integer.
12.34; // A decimal number

Strings

"I am a string";
""; // The empty string.
"123"; // This is a string, not a number.

No Value

nil

Expressions

Arithmetic

add + me;
subtract - me;
multiply * me;
divide / me;

-negateMe;

Comparison and Equality

Comparison Operators.

less < than;
lessThan <= orEqual;
greater > than;
greaterThan >= orEqual;

1 == 2; // false.
"cat" != "dog"; // true

314 == "pi"; // false

123 == "123"; // false

Logical operators

!true; // false.
!false; // true.

true and false; // false.
true and true; // true.

false or false; // false.
true or false; // true.

Precedence and Grouping

var average = (min + max) / 2;

Statements

print "Hello, world!";

{
    print "One statement.";
    print "Two statements.";
}

Variables

var breakfast 	= "bagels";
print breakfast; // "bagels".

breakfast 	= "beignets";
print breakfast; // "beignets".

Control Flow

if

if (condition) {
    print "yes";
} else {
    print "no";
}

while

var a = 1;

while (a < 10) {
    print a;
    a = a + 1;
}

for

for (var a = 1; a < 10; a = a + 1) {
    print a;
}

Functions

// Functions that take arguments
makeBreakfast(bacon, eggs, toast);

// Functions that do not toake arguments
makeBreakfast();

fun keyword

fun printSum(a, b) {
    print a + b;
}

fun returnSum(a, b) {
    return a + b;
}

Closures

fun addPair(a, b) {
    return a + b;
}
fun identity(a) {
    return a;
}

print identity(addPair)(1, 2); // Prints "3"

fun outerFunction() {
    fun localFunction() {
        print "I'm local!";
    }
    localFunction();
}

fun returnFunction() {
var outside = "outside";
    
    fun inner() {
        print outside;
    }
    
    return inner;
}

var fn = returnFunction();
fn();

Classes

// The body of a class contains its methods.
// They look like function declarations but without the fun keyword.
class Breakfast {
    
    cook() {
        print "Eggs frying!";
    }
    
    serve(who) {
        print "Enjoy your breakfast, " + who + ".";
    }
    
}

Classes are First Class

// Storing Classes in Variables.
var someVariable = Breakfast;

// Passing Classes to Functions.
someFunction(Breakfast);

Class Instances

// Calling a class like a function, produces a new instance of itself.
var breakfast = Breakfast();
print breakfast; // "Breakfast instance".

Instantiation and Initialization

// Assigning to a field creates it if it doesn’t already exist
breakfast.meat = "sausage";
breakfast.bread = "sourdough";

// If you want to access a field or method on the current object
// from within a method, you use good old this.

class Breakfast {
    serve(who) {
        print "Enjoy your " + this.meat + " and " +
        this.bread + ", " + who + ".";
    }
    // ...
}

class Breakfast {
    init(meat, bread) {
        this.meat = meat;
        this.bread = bread;
    }
    // ...
}

var baconAndToast = Breakfast("bacon", "toast");

baconAndToast.serve("Dear Reader");
// "Enjoy your bacon and toast, Dear Reader."

Inheritance

class Brunch < Breakfast {
    drink() {
        print "How about a Bloody Mary?";
    }
}

// Every method defined in the superclass is also available to its subclasses.
var benedict = Brunch("ham", "English muffin");
benedict.serve("Noble Reader");

// Even the init() method gets inherited.
// In practice, the subclass usually wants to define its own init() method too.
class Brunch < Breakfast {
    init(meat, bread, drink) {
        super.init(meat, bread);
        this.drink = drink;
    }
}