The document presents a discussion on developing Android applications using the Ceylon programming language, highlighting the limitations of Java and the advantages of Ceylon, such as first-class functions, higher-order functions, and a more robust type system. Examples of using union and intersection types, task serialization, and type-safe null handling are provided to illustrate Ceylon's features. The author, Enrique Zamudio, also emphasizes community resources and ways to engage with Ceylon's development.

1. Developing Android
applications with
Ceylon
Enrique Zamudio
@chochosmx
github.com/chochos
@ceylonlang
#CeylonLang

2. • Programming since 1982
• Professionally since 1994
• Java since 2000
• FOSS projects:
• j8583
• jAlarms
• Ceylon
• Java Champion 2015

3. Why Ceylon?
• Many Android devs are not too keen on Java
• Some don't even consider it to be a "real" Java
• Type system is somewhat limited
• Lots of anonymous classes throughout
codebase

4. Ceylon advantages
• Functions are first-class citizens
• Higher-order functions
• Union and intersection types
• Easier to manage generics
• No checked exceptions
• More typesafe (typesafer?) than Java
• Typesafe null, bounded generics

5. User|LoginError login(
String username,
String password);
String password);
String password);
Union type

6. if (is User r = login(u,p)) {
//it's a user
print(r.username);
} else {
//it's an error
print(r.reason);
}
}
}
}
}
}

7. Object obj = ...;
if (obj instanceof Foo) {
print(((Foo)obj).foo);
}
}
}
}

8. Object obj = ...;
if (obj instanceof Foo) {
print(((Bar)obj).bar);
}
}
}
}

9. Serializing
Runnables

10. void send(??? task) {
//send task over the wire
//is run on the other side
}
}
}
}

11. interface MyTask
extends Runnable,
Serializable {}
Serializable {}
Serializable {}

12. void send(MyTask task) {
//send task over the wire
//is run on the other side
}
}
}
}

13. class WeirdlyNamedApacheTask
implements Runnable,
Serializable {
...
}
}
}
}
}

14. class CumbersomeWrapper
implements MyTask {
final WeirdlyNamedApacheTask
wrappedTask;
}
}
}
}
}

15. void send(
Runnable & Serializable task) {
//send task over the wire
//is run on the other side
}
}
}
}
}

16. void send(
Runnable & Serializable task) {
//send task over the wire
//is run on the other side
}
}
}
}
}
Intersection type

17. null

18. ObjectObjectObjectObject

19. ObjectObjectObjectObject NullNullNullNull

20. ObjectObjectObjectObject NullNullNullNull
AnythingAnythingAnythingAnything

21. ObjectObjectObjectObject NullNullNullNull
AnythingAnythingAnythingAnything
StringStringStringString NumberNumberNumberNumber

22. ObjectObjectObjectObject NullNullNullNull
AnythingAnythingAnythingAnything
StringStringStringString NumberNumberNumberNumber nullnullnullnull

23. String s = null;
Integer s = null;
Null n = null;
Null n = null;
Null n = null;

24. String s = null;
Integer s = null;
Null n = null;
Null n = null;
Null n = null;
✘

25. String | Integer
String | Null
String | Null
String | Null

26. String|Integer a = 1;
String|Integer b = "one";
String|Null s1 = "s";
String|Null s2 = null;
;
;
;
;

27. String|Integer a = 1;
String|Integer b = "one";
String? s1 = "s";
String? s2 = null;
;
;
;
;

28. String? s = foo();
print(s.size); //WON'T COMPILE
if (exists s) {
...
}
}
}
}
}

29. ObjectObjectObjectObject NullNullNullNull
AnythingAnythingAnythingAnything
StringStringStringString NumberNumberNumberNumber nullnullnullnull

30. Algebraic
(enumerated) types
(enumerated) types

31. of Object|Null
class Null of null
object null extends Null
Null
Null
Null
Null

32. class Boolean
of true|false
class Comparison
of larger|smaller|equal
larger|smaller|equal
larger|smaller|equal
larger|smaller|equal
larger|smaller|equal

33. ObjectObjectObjectObject NullNullNullNull
AnythingAnythingAnythingAnything
StringStringStringString NumberNumberNumberNumber nullnullnullnull

34. Bottom type

35. ObjectObjectObjectObject NullNullNullNull
AnythingAnythingAnythingAnything
NothingNothingNothingNothing
NumberNumberNumberNumberStringStringStringString nullnullnullnull

36. Iterable<String,Nothing>
Object & Null
Nothing
Nothing
Nothing
Nothing
Nothing
Nothing

37. Demo time!

38. Code dive

39. ¿?

40. try.ceylon-lang.org
github.com/ceylon
@ceylonlang
enrique@ceylon-lang.org
@chochosmx
gitter.im/ceylon