Ceylon is a new programming language for the JVM which was recently released on http://ceylon-lang.org with Eclipse based tooling available from day one. This talk will introduce you to the goals and some of the features of the language while showing the features of the Eclipse based IDE. Ceylon is a programming language for writing large programs in a team environment. The language is elegant, highly readable, extremely typesafe, and makes it easy to get things done. And it's easy to learn for programmers who are familiar with mainstream languages used in business computing. Ceylon has a full-featured Eclipse-based development environment, allowing developers to take best advantage of the powerful static type system. Programs written in Ceylon execute on the JVM. Slides as they were used at EclipseCon 2012

1. the language and its tools
Max Rydahl Andersen
Red Hat
http://about.me/maxandersen
EclipseCon 2012

2. About Me
• Max Rydahl Andersen
• Lead of JBoss Tools & Developer Studio
• Committer on Hibernate Core, Seam & Weld
• Co-host of JBoss Community Asylum Podcast
• @maxandersen on Twitter
• http://about.me/maxandersen

3. Ceylon Origins
• Created and lead by Gavin King
• Helped by others at JBoss
• Frustrated love for Java
• Lessons learned working in JCP
• Starting blocks
• on the JVM
• in the spirit of Java
• practical
• Slashdotted (with no web site)

4. Language Introduction
z

5. doc "A familiar Rectangle"
class SimpleRectangle() {
Integer width = 0;
Integer height = 0;
function area() {
return width * height;
}
}

6. doc "A real Rectangle."
shared class Rectangle(Integer width, Integer
height) {
// initializer
if(width <=0 || height <=0) {
throw;
}
shared Integer width = width;
shared Integer height = height;
shared Integer area() {
return width * height;
}
}

7. Modular by default
package com.acme.dotcom.domain package com.acme.dotcom.business
shared class Foo class Woo shared class Action class Reaction
shared String bar() shared String war() shared String ping() String pong()
String baz() String waz()

8. Immutable by default
Integer width = w;

9. Immutable by default
Integer width = w;
variable Integer width := w;

10. doc "A variable Rectangle with properties."
shared class VariableRectangle(Integer w,
Integer h) {
shared variable Integer width := w;
shared variable Integer height := h;
shared Integer badArea {
return width * 42;
} Text
assign badArea {
width := badArea/42;
}
shared actual String string {
return "w:" width ",h:" height "";
}
}

11. shared class
Point(Integer x, Integer y) {
shared Integer x = x;
shared Integer y = y;
}
shared class
Point3D (Integer x, Integer y, Integer z)
extends Point(x, y) {
shared Integer z = z;
}

12. Integer attribute = 1;
Integer attribute2 { return 2; }
void topmethod(){}
interface Interface{}
class Class(Integer x){
Integer attribute = x;
Integer attribute2 { return x; }
class InnerClass(){}
interface InnerInterface{}
void method(Integer y){
Integer attribute = x;
Integer attribute2 { return y; }
class LocalClass(){}
interface LocalInterface{}
void innerMethod(Integer y){}
}
}

13. No
NullPointerException’s
void typesafety() {
Rectangle? rectOrNoRect() { return null; }
Rectangle? rect = rectOrNoRect();
print(rect.string); // compile error
if(exists rect) {
print(rect.string);
} else {
print("No rectangle");
}
}

14. What is in a
Type ?

15. Union Type
• To be able to hold values among a list of
types
• We must check the actual type before use
• `TypeA|TypeB`
• `Type?` is an alias for `Type|Nothing`

16. class Apple()
{ shared void eat() { print("Eat " this ""); }}
class Broccoli()
{ shared void throwAway() { print("Throw " this ""); } }
void unions() {
Sequence<Apple|Broccoli> plate =
{Apple(), Broccoli()};
for (Apple|Broccoli food in plate) {
print("Looking at: " food.string "");
if (is Apple food) {
food.eat();
} else if (is Broccoli food) {
food.throwAway();
}
}
}

17. Intersection Type
interface Food { shared formal void eat(); }
interface Drink { shared formal void drink(); }
class Guinness() satisfies Food & Drink {
shared actual void drink() {}
shared actual void eat() {}
}
void intersections(){
Food & Drink specialStuff = Guinness();
specialStuff.drink();
specialStuff.eat();
}

18. No Overloading

19. No Overloading
• WTF!?

20. No Overloading
• WTF!?
• is overloading evil ?

21. No Overloading
• WTF!?
• is overloading evil ?

22. No Overloading
• WTF!?
• is overloading evil ?
• Only usecase:
• Optional parameters
• Work on different subtypes

23. class
Rectangle(Integer width = 2, Integer height = 3) {
shared Integer area(){
return width * height;
}
}
void method() {
Rectangle rectangle = Rectangle();
Rectangle rectangle2 = Rectangle {
width = 3;
height = 4;
};
}

24. interface Shape2D of Triangle|Circle|Figure2D {}
class Triangle() satisfies Shape2D {}
class Circle() satisfies Shape2D {}
class Figure2D() satisfies Shape2D {}
void workWithRectangle(Triangle rect){}
void workWithCircle(Circle circle){}
void workWithFigure2D(Figure2D fig){}
void supportsSubTyping(Shape2D fig) {
switch(fig)
case(is Triangle) {
workWithRectangle(fig);
}
case(is Circle) {
workWithCircle(fig);
}
case(is Figure2D) {
workWithFigure2D(fig);
}
}

25. Other features
• Interface based Operator overloading
• Closures
• Annotations
• Type aliases
• Meta-model
• Interception
• Interface with default implementations / “multiple inheritance”
• Declarative syntax for datastructures
• ...and more

26. Table table = Table {
title="Squares";
rows=5;
border = Border {
padding=2;
weight=1;
};
Column {
heading="x";
width=10;
String content(Natural row) {
return row.string;
}
},
Column {
heading="x**2";
width=12;
String content(Natural row) {
return (row**2).string;
}
}
};

27. Ceylon Today
• Website (http://ceylon-lang.org)
• Active and growing community
• Fully open source (http://github.com/ceylon)
• Targets JVM and JS (http://try.ceylon-lang.org)
• Milestone 2 just released
• Java interopability
• Full IDE support

28. Ceylon IDE

29. Ceylon IDE
• Incremental compiler and error reporting
• Full editor with outline, folding and navigation
• Refactoring, Quick fixes, Search
• Wizards, Module repository integration
• Debugging

30. Ceylon IDE -
Behind the Scenes
• Considered XText, DLTK, IMP & “DIY”
• XText - very complete, but does not allow Antlr
and require XText custom parser and
typechecker
• DLTK - allows Antlr, but at the time no good
documentation and a preference to by “too
dynamic language focused”
• IMP - allows antlr and custom typechecker and
just worked, but..

31. Ceylon IDE -
Next Steps
• IMP has many limitations when you push it
• XText still too much “XText”
• DLTK looks interesting
• End result probably a mix of the above in a
“DIY” solution
• Contributors welcome!

32. Ceylon - Tomorrow
• M3:
• - Annotations
• - Reified type parameters
• - Interception
• - Meta-model
• <Your Name Here>

33. ?
• http://try.ceylon-lang.org
• http://ceylon-lang.org
• http://ceylon.github.com/
Text
Text
bit.ly/ec12ceylon