Racket is a ProgrammingLanguage (and implementation) descended from SchemeLanguage, including an IDE and a large number of built in libraries and tools. Racket also includes several secondary language dialects including R5RS, R6RS, lazy and typed variants, and teaching languages.

Racket is the project formerly known as PltScheme, and the programs DrScheme (The IDE) and MzScheme (The interpreter) are now DrRacket and Racket. Details on the renaming are at http://racket-lang.org/new-name.html and details on the language dialects at http://docs.racket-lang.org/guide/dialects.html.

The Racket language is based on R5RS Scheme, but includes way more features in the base language:

* PatternMatching a la MlLanguage, extensible
* Optional StaticTyping thanks to TypedRacket
* RegularExpression support
* Class system (No CLOS, though Swindle contains a CLOS-like system)
* LispMacros
* HygienicMacros as in SchemeLanguage
* extensive facilities for creating languages http://docs.racket-lang.org/guide/languages.html


This is on top of all expected features of SchemeLanguage. See the TOC of the guide at http://docs.racket-lang.org/guide/index.html.

Racket is presently very BatteriesIncluded. You can get a feature overview at the documentation index: http://docs.racket-lang.org/

Built-in libraries of interest (to me):
* Built-in lexer/parser
* Hazy OpenGl 1.5 support (''I'' use it)
* Cross-platform GUI toolkit
* Built in web server & web framework... ish... thing -- ''which supports WebTransactionsWithContinuations using SchemeLanguage'''''''s FirstClassContinuation''''''s. See ProgrammingLanguagesApplicationAndInterpretation by the designer of the Racket webserver.''
* XML and HTML parsers
* CeeLanguage FFI

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Racket has a recent story about a successful low-level language to high-level language rewrite. As of Racket 5.1, the graphics layer has been rewritten from 200,000 lines of CeePlusPlus to 30,000 lines of RacketLanguage on newer and better libraries. (http://blog.racket-lang.org/2010/12/racket-version-5.html)

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Performance-wise, Racket seems to currently (early 2011) be running only slightly slower (2-3x) than the statically typed languages like JavaLanguage and HaskellLanguage. This is according to the ComputerLanguageBenchmarksGame. This places it faster than any other dynamic language on the list. 

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CategoryScheme