Dr Racket - Features

Features

Racket's core language includes macros, modules, lexical closures, tail calls, delimited continuations, parameters (fluid variables), software contracts, green and OS threads, and more. The language also comes with primitives, such as eventspaces and custodians, which control resource management and enables the language to act like an operating system for loading and managing other programs. Further extensions to the language are created with the powerful macro system, which together with the module system and custom parsers can control all aspects of a language. Unlike programming languages that lack macro systems, most language constructs in Racket are written on top of the base language using macros. These include a mixin class system, a component (or module) system as expressive as ML's, and pattern matching.

In addition, the language features the first contract system for a higher-order language. Racket's contract system is inspired by the Design by Contract work for Eiffel and extends it to work for higher-order values such as first-class functions, objects, reference cells, and so on. For example, an object that is checked by a contract can be insured to make contract checks when its methods are eventually invoked.

Racket's compiler is a bytecode compiler that translates to an internal bytecode format that is run by the Racket virtual machine. On x86 and PowerPC platforms, the bytecode is further compiled using a JIT compiler at runtime.

Since 2004, the language has also shipped with PLaneT, a package manager that is integrated into the module system so that third-party libraries can be transparently imported and used. Additionally, PLaneT has a built-in versioning policy to prevent dependency hell.