Ceylon 1.2.2 is now available

Four months after the last major release, and exactly one month after the 1.2.1 update, Ceylon 1.2.2 is a new maintenance release, with over 70 issues closed, including new features, improvements and bug fixes such as:

  • you can now use java.lang.Iterable and Java arrays in for statements and comprehensions,
  • the [] lookup operator works on Java lists, maps, and arrays,
  • the in operator works on java.util.Collection and, last but not least,
  • a new ceylon bootstrap command to make it really easy to distribute code to people that don't have Ceylon installed.

Note that for the JVM backend, this release is backwards-compatible with the previous releases (1.2.0 and 1.2.1), which means you can use modules compiled with 1.2.0 on a 1.2.2 distribution out of the box. This is not as easy the other way around, if you want to run modules compiled for 1.2.2 on a 1.2.0 distribution, which is why we recommend you upgrade to 1.2.2.

Sadly, on the JavaScript backend, we had to break binary compatibility to fix serious interoperation issues, and so modules compiled for 1.2.2 and 1.2.0 are not compatible. Versions 1.2.1 and 1.2.2 are binary compatible but can still give problems when used together. We recommend you upgrade your distribution to 1.2.2 and recompile your modules.

About Ceylon

Ceylon is a modern, modular, statically typed programming language for the Java and JavaScript virtual machines. The language features a flexible and very readable syntax, a unique and uncommonly elegant static type system, a powerful module architecture, and excellent tooling, including an awesome Eclipse-based IDE.

Ceylon enables the development of cross-platform modules that execute portably in both virtual machine environments. Alternatively, a Ceylon module may target one or the other platform, in which case it may interoperate with native code written for that platform.

In the box

This release includes:

  • a complete language specification that defines the syntax and semantics of Ceylon in language accessible to the professional developer,
  • a command line toolset including compilers for Java and JavaScript, a documentation compiler, a test runner, a WAR archive packager, and support for executing modular programs on the JVM and Node.js,
  • a powerful module architecture for code organization, dependency management, and module isolation at runtime,
  • the language module, our minimal, cross-platform foundation of the Ceylon SDK, and
  • a full-featured Eclipse-based integrated development environment.


Ceylon is a highly understandable object-oriented language with static typing. The language features:

  • an emphasis upon readability and a strong bias toward omission or elimination of potentially-harmful or potentially-ambiguous constructs and toward highly disciplined use of static types,
  • an extremely powerful and uncommonly elegant type system combining subtype and parametric polymorphism with:
    • first-class union and intersection types,
    • both declaration-site and use-site variance, and
    • the use of principal types for local type inference and flow-sensitive typing,
  • a unique treatment of function and tuple types, enabling powerful abstractions, along with the most elegant approach to null of any modern language,
  • first-class constructs for defining modules and dependencies between modules,
  • a very flexible syntax including comprehensions and support for expressing tree-like structures,
  • fully-reified generic types, on both the JVM and JavaScript virtual machines, and a unique typesafe metamodel.

More information about these language features may be found in the feature list and quick introduction.


Ceylon IDE now features the following improvement, along with bugfixes:

  • support for the ceylon bootstrap command


The platform modules, recompiled for 1.2.2, are available in the shared community repository, Ceylon Herd.

This release introduces a single new platform module:

  • ceylon.buffer is a cross-platform module for converting between text and binary forms of data.

Along with some enhancements to existing modules:

  • ceylon.file now has functions for creating temporary files and directories,
  • ceylon.net now has support for template handlers,
  • ceylon.html was rewritten according to HTML5 specification and with support for lazy evaluation.


You can try Ceylon using the Web IDE, featuring syntax highlighting, interactive error reporting, autocompletion, online documentation, and persistence and code sharing via Gist.

The Web IDE serves a dual purpose as a standard example demonstrating the use of Ceylon for web application development and deployment to the OpenShift cloud platform.


The Ceylon community site, http://ceylon-lang.org, includes documentation, and information about getting involved.

Source code

The source code for Ceylon, its specification, and its website, is freely available from GitHub.

Information about Ceylon's open source licenses is available here.


Bugs and suggestions may be reported in GitHub's issue tracker.

Migrating from Ceylon 1.2.0

Migration from Ceylon 1.2.0 is easy. To recompile a module for 1.2.2:

  • First ensure that its dependencies have also been recompiled.
  • If it imports a Ceylon SDK platform module, upgrade the version number specified by the module import statement from "1.2.0" to "1.2.2" .
  • If it was compiled against Ceylon 1.2.0 you should still be able to use it in 1.2.2 for the JVM backend, as it is backwards-compatible. Sadly, this is not the case for the JavaScript backend, and so you will need to recompile your modules with 1.2.2.


As always, we're deeply grateful to the community volunteers who contributed a substantial part of the current Ceylon codebase, working in their own spare time. The following people have contributed to Ceylon:

Gavin King, Stéphane Épardaud, Tako Schotanus, Tom Bentley, David Festal, Enrique Zamudio, Bastien Jansen, Emmanuel Bernard, Aleš Justin, Tomáš Hradec, James Cobb, Ross Tate, Max Rydahl Andersen, Mladen Turk, Lucas Werkmeister, Roland Tepp, Diego Coronel, Matej Lazar, John Vasileff, Toby Crawley, Julien Viet, Loic Rouchon, Stephane Gallès, Ivo Kasiuk, Corbin Uselton, Paco Soberón, Michael Musgrove, Daniel Rochetti, Henning Burdack, Luke deGruchy, Rohit Mohan, Griffin DeJohn, Casey Dahlin, Gilles Duboscq, Tomasz Krakowiak, Alexander Altman, Alexander Zolotko, Alex Szczuczko, Andrés G. Aragoneses, Anh Nhan Nguyen, Brice Dutheil, Carlos Augusto Mar, Charles Gould, Chris Gregory, klinger, Martin Voelkle, Mr. Arkansas, Paŭlo Ebermann, Vorlent, Akber Choudhry, Renato Athaydes, Flavio Oliveri, Michael Brackx, Brent Douglas, Lukas Eder, Markus Rydh, Julien Ponge, Pete Muir, Nicolas Leroux, Brett Cannon, Geoffrey De Smet, Guillaume Lours, Gunnar Morling, Jeff Parsons, Jesse Sightler, Oleg Kulikov, Raimund Klein, Sergej Koščejev, Chris Marshall, Simon Thum, Maia Kozheva, Shelby, Aslak Knutsen, Fabien Meurisse, Sjur Bakka, Xavier Coulon, Ari Kast, Dan Allen, Deniz Türkoglu, F. Meurisse, Jean-Charles Roger, Johannes Lehmann, allentc, Nikolay Tsankov, Chris Horne, Gabriel Mirea, Georg Ragaller, Harald Wellmann, Oliver Gondža, Stephen Crawley, Byron Clark, Francisco Reverbel, Jonas Berlin, Luke Hutchison, Nikita Ostroumov, Santiago Rodriguez, Sean Flanigan.