The Racket programming language project has released Racket version 9.0. Racket is a descendant of Scheme, so it is part of the Lisp family of languages. The headline feature in the release is parallel threads, which adds to the concurrency tools in the language: "While Racket has had green threads for some time, and supports parallelism via futures and places, we feel parallel threads is a major addition." Other new features include the black-box wrapper to prevent the compiler from optimizing calculations away, the decompile-linklet function to map linklets back to an s-expression, the addition of Weibull distributions to the math library, and more.