This site provides documentations about Programming Language Onion.

Onion is an object-oriented and statically typed programming language. Source codes of Onion compiles into JVM class files (in memory / file).

Originally, Onion compiler was written in Java in 2005. Recently, It has been rewritten in Scala completely except Parser since JavaCC is used.

Old document is available from the site. Note that they have several differences from current Onion (Onion-0.2-M1).