PLT Scheme is an innovative programming language that builds on a rich academic and practical tradition.
It is suitable for implementation tasks ranging from scripting to application development, including GUIs, web services, etc.
It includes the DrScheme programming environment, a virtual machine with a just-in-time compiler, tools for creating stand-alone executables, the PLT Scheme web server, extensive libraries, documentation for both beginners and experts, and more.
It supports the creation of new programming languages through a rich, expressive syntax system. Example languages include Typed Scheme, ACL2, FrTime, Lazy Scheme, and ProfessorJ (which is a pedagogical dialect of Java).
Getting started:

Download PLT Scheme


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Latest release: 4.2.5, April 2010