CeylonReadability for the Modern Java Developer

History• Red Hat’s, Gavin King

• Readability

• Harmful constructs

• 1.0.0 (Nov. 2013)

• 1.1.0 (Oct. 2014)

• Sri Lanka (1972)

Names, bindings, scoping• Case-sensitive

• Immutable by default

• Static scoping (Exception: JS)

Data Types• All objects (no primitives)

• Integer, Float, String

• Postfix “?” allows for null

• Postfix “+” must contain a value

• Postfix “*” denotes sequential (Iterating over arguments)

• “value” keyword for type inference

• Intersection and Union types ( & |)

• “alias” keyword

Expression and Assignments• Same as Java

• Pure, first-order functions (no object burden)

• <keyword(s)> <type> <id> = <value> || <function>;

{String*} & Correspondence<Integer,String> strings = [“Hello”,”world”];

String? str = strings.get(0); //Call get() of Correspondence

Integer size = strings.size; //Call size of Iterable

Control Structures• If, switch, assert, for, while, try-catch

• Curly braces regardless of number of lines

• C-style for loops unnecessary (use range operator)

• For-loops can have “else” block, optionally

• No do-while

• Remove type to infer exception type

Subprograms• Abstracted from “Callable” interface

• shared interface Callable<out Return, in Arguments>

given Arguments satisfies Anything[]{ }

Abstraction and Encapsulation• Helps ease “this” usage• No “new” keyword for instantiation

"A polar coordinate" //Class annotation class Polar(Float angle, Float radius) {

shared Polar rotate(Float rotation) => Polar(angle+rotation, radius); shared Polar dilate(Float dilation) => Polar(angle, radius*dilation); shared String description

= "(``radius``,``angle``)"; } print(Polar(0.37, 10.0).description);

OOP Support• Ceylon supports “impure” OOP

• Lack of structural polymorphism

• Class is a constructor that produces a new instance of a given type

Concurrency• Concurrent models unavailable by default

• Must use Java or a 3rd party module

Readability• Familiar syntax

• Static typing for better understanding

• Annotations

• Hard for newer users to get used to heavy, static typing

Writability• Expressiveness is encouraged when writing in Ceylon

• Great workflow

• Functions and fields can be written as standalone (no class needed)

• Standalones compiled into classes within the “.car” file

Reliability• Runs on the JVM

• Static typing allows for much greater reliability

• Immutable nature also enhances reliability

Cost• Free plug-in for Eclipse

• Open source

• Relies on JVM (resource intensive)

Extras• Uses modules

• Ceylon Herd

• Java and Javascript can be fully integrated into Ceylon code

• Ceylon code can be compiled to JS code natively

Questions• Do you have them?