Tags give the ability to mark specific points in history as being important
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v5.3.6
ded0c4a8 · ·Racket v5.3.6 Racket v5.3.6 is a bug-fix release. It eliminates errors from v5.3.5 that people have found over the summer.
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v5.3.5
722dc826 · ·Racket v5.3.5 This is a special-purpose release to match the arrival of "Realm of Racket" in bookstores. Racket v.5.3.5 adds a single `realm' collection to the v5.3.4 release. The new collection contains the source code that readers of Realm may wish to use for experiments.
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v5.3.4
43d5976b · ·Racket v5.3.4 * Extflonums (80-bit floating-point numbers) are supported on some x86/x86_64 platforms -- including Windows, and including platforms where Racket is compiled to use SSE instructions for flonum arithmetic. Thanks to Michael Filonenko. * OS X: DrRacket and all of the other apps are now signed with an official key. * Tally Maze: a new game based an enumeration of 2d mazes. * The Optimization Coach, a DrRacket plugin, has been moved from the Racket distribution to the Racket package repository. Install it with: raco pkg install optimization-coach * Redex: `define-union-language' now merges productions when languages define the same nonterminals. Thanks to William Bowman. * The `srfi/19' library is now compatible with the date structure type exported by `racket/base'.
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v5.3.3
ca400d68 · ·Racket v5.3.3 This is a bug-fix release to address a flaw in DrRacket v5.3.2 concerning interactions between the contour window and the syntax coloring.
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v5.3.2
df147de3 · ·Racket v5.3.2 Core Libraries: * The new `math' library provides functions and data structures for working with numbers and collections of numbers. Functions include non-elementary (such as gamma, zeta, Lambert's W), number-theoretic (factorization, modular arithmetic), linear algebra (arithmetic, decompositions), and statistical (expected values, order statistics, binning). Data structures include arbitrary-precision bigfloats, probability distributions, and multidimensional arrays. * The new `file/untar', `file/untgz', and `file/unzip' libraries support unpacking widely used archive formats. * The new `lazy-require' form allows programs to delay the loading and instantiation of helper modules until they are needed. * The new `data/bit-vector' library provides an implementation of bit vectors (a mutable sequence of booleans) supporting popcount. * The `racket/generic' library allows the specification of default method implementations for core datatypes. * The `openssl' library can verify hostnames and use the operating system's certificate store to verify certificates. Package System: * A new package system is in beta release. This system will become Planet's successor. It differs significantly from the latter. For details, please read the documentation at http://docs.racket-lang.org/planet2/ and list your packages on the new index at https://pkg.racket-lang.org/. * The `raco test' command supports testing by collection and package, in addition to by directory and file, with the "-c" and "-p" options. Teaching Libraries: * batch-io: the read and write functions work on Unix-style standard input and output. DrRacket: * DrRacket's GUI is more responsive. * The automatic parenthesis insertion mode is improved. Scribble: * Scribble renders Markdown format files via the "--markdown" command-line flag. Example use case: Generate documentation hosted on GitHub or BitBucket. * Documentation cross-reference information is stored in an SQLite3 database, which means that SQLite3 is required for building Racket documentation on Unix/Linux machines (but SQLite3 is included in Racket distributions for Windows and Mac OS X). Using a database for cross-reference information significantly reduces the initial footprint of DrRacket, since DrRacket no longer needs to load all cross-reference information. Typed Racket: * Typed Racket programs can require `plot/typed' to draw plots. List- and vector-accepting functions accept general sequences. * Typed Racket supports Racket's delimited continuation and continuation mark operators. Redex: * Added more support for `define-judgment-form', including random generation for well-formed judgments and visualization of judgments. Deprecation: The following have been removed in this release: * the `planet' command-line tool; use `raco planet' instead. The following has been deprecated and will be removed in the August 2013 release: * the `mzlib/class100' library; use `racket/class' instead.
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v5.3.1
2f4c6774 · ·Racket v5.3.1 Racket: * The `case' form dispatches on characters, fixnums, symbols, and keywords in logarithmic time. (Thanks to Jon Zeppieri.) * The new `racket/format' library provides new and improved string-formatting functions. * Logging tools include improved filtering support based on the name of a logger. A new `define-logger' form simplifies the use of named loggers. Forms such as `log-debug' now support string formatting. * The `for' forms now support `#:break' and `#:final' clauses. * The new PLTCOMPILEDROOTS environment variable configures the search path for compiled bytecode. DrRacket: * Check Syntax now summarizes the documentation (i.e., the blue boxes) for the identifier at the insertion point in the top-right corner of the definitions window. * Check Syntax now runs continuously for programs that declare their language within the source. This mode has been available for several of the past releases, but now enabled by default. * DrRacket can spell-check string constants (enable this in the Edit menu). Typed Racket: * Typed Racket interprets the Any type as a different contract. This may signal dynamic errors in some existing mixed typed/untyped programs. The normal fix is to replace a use of Any with a more specific types. * NaN is included in all of Typed Racket's floating-point types, which makes precise floating-point types easier to use. * Typed Racket supports a `cast' operation with support for higher-order types. * Typed Racket provides the `:query-type/args' and `:query-type/result' utilities to explore types at the REPL. Miscellaneous: * The `compatibility' collection provides features from Racket relatives, such as `defmacro' and mutable lists. These features are provided to ease porting code to Racket. Avoid them in modern Racket code. * Screenshots of the widgets provided by the Racket GUI library are included in the documentation. (Thanks to Diogo F. S. Ramos.) * FrTime was ported to racket lang. (Thanks to Patrick Mahoney.) Deprecation: The following has been deprecated and will be removed in the January 2013 release: * the `planet' command-line tool; use `raco planet' instead. The following has been deprecated and will be removed in the August 2013 release: * the `mzlib/class100' library; use `racket/class' instead.
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v5.3
d8dc0874 · ·Racket v5.3 * Submodules are nested module declarations that can be loaded and run independently from the enclosing module. For an overview of submodules, see http://blog.racket-lang.org/2012/06/submodules.html * The futures visualizer is a graphical profiling tool for parallel programs using futures. The tool shows a detailed execution timeline depicting the migration of futures between threads, and gives detailed information about each runtime synchronization that occurred during program execution. In addition, `would-be-future' is a special type of future that always executes sequentially and records all potential barricades a regular future would encounter. * Optimization Coach (formerly Performance Report) reports information about Racket's inlining optimizations. Optimization Coach can be launched in any language through the View menu. * The new `images/flomap' library defines floating-point bitmaps and fast image processing operations on them. It is written in Typed Racket, so Typed Racket code may use it without the cost of contract checks. * The new `json' library supports parsing and generating JSON. (Originally based on Dave Herman's planet library.) * `racket/string' is extended with a set of simplified string manipulation functions that are more convenient than using regexps. `regexp-match*' and friends can now be used with new keyword arguments to return specific matched regexp group/s and gaps between matches. * The new `racket/generic' library allows generic function definitions, which dispatch to methods added to a structure type via the new `#:methods' keyword. * The `class' form supports declaring a method abstract. An abstract method prevents a class from being instantiated unless it is overridden. * The contract library comes with support for interfaces, generics, prompts, continuation-marks, and structs. * Most error messages use a new multi-line format that is more consistent with contract errors and accommodates more information. * Typed Racket supports function definitions with keyword arguments; the startup time of Typed Racket programs has been sharply reduced. * The new `ffi/com' library replaces MysterX; a compatibility `mysterx' library remains, but without ActiveX support. The new `ffi/unsafe/com' library offers a more primitive and direct way to use COM classes and methods. * There is now a very complete completion code for zsh. It is not included in the distribution though; get it at http://goo.gl/DU8JK (This script and the bash completions will be included in the standard installers in future versions.) --- DEPRECATION ---------------------------------------------------- Effective this release: - The `tex2page' and `combinator-parser' libraries have been moved from the Racket distribution to PLaneT: (require (planet plt/tex2page)) (require (planet plt/combinator-parser)) The following has been deprecated and will be removed in the January 2013 release: - the `planet' command-line tool; use `raco planet' instead. The following has been deprecated and will be removed in the August 2013 release: - the `mzlib/class100' library; use `racket/class' instead. -
v5.2.1
0a3fcb20 · ·Racket v5.2.1 * Performance improvements include the use of epoll()/kqueue() instead of select() for the Racket thread scheduler, cross-module inlining of small functions, and the use of SSE instead of x87 for JIT-compiled floating-point operations on platforms where SSE is always available (including x86_64 platforms). A related change is the interning of literal numbers, strings, byte strings, characters, and regexps that appear in code and syntax objects. * DrRacket uses a set of composable ray-traced icons available from the new `images' library collection. * Typed Racket's `typecheck-fail' form allows macro creators to customize the error messages that Typed Racket produces. This is especially useful when creating pattern matching macros. * The performance of Redex's matcher has been substantially improved; depending on the model you should see improvements between 2x and 50x in the time it takes to reduce terms. * Plots look nicer and are more correct at very small and very large scales. New features include customizable dual axis ticks and transforms (e.g., log axes, date and currency ticks, axis interval collapse and stretch), stacked histograms, and 3D vector fields. The legacy `fit' function and libfit have been removed. * The `2htdp/universe' library's `big-bang' form supports an experimental game pad key handler. * The `db' library now supports nested transactions and PostgreSQL arrays. Bugs involving MySQL authentication and memory corruption in the SQLite bindings have been fixed. * The Macro Stepper tool in DrRacket no longer executes a program after expanding it. * In the DMdA teaching languages, infinite recursive signatures ("streams", for example) with no intervening `mixed' are now supported, and the signatures of record definitions without fields now have generators for use with `property'. * MysterX's ActiveX support is deprecated and will be removed in the next release. MysterX's core COM functionality will become deprecated in the next release, but COM functionality will be supported for the foreseeable future as a compatibility layer over a forthcoming `ffi/com' library. -
v5.2
e42bfe36 · ·Racket v5.2 Release Highlights: * DrRacket comes with an experimental, on-line check syntax tool, although this new tool is disabled default. See below for more information. * The new `db' library offers a high-level, functional interface to popular relational database systems, including PostgreSQL, MySQL, and SQLite, as well as other systems via ODBC. * A new XREPL collection provides convenient commands for a plain racket REPL. It is particularly convenient for people who prefer console-based work and alternative editors. See also the new chapter on command-line tools and other editors at the end of the Racket Guide. * The `plot' collection has been reimplemented in Racket. It now offers PDF output, log axes, histograms, and more. Some code that uses `plot' will still work, and some will need light porting. The `plot/compat' module offers expedient backward compatibility. * DrRacket uses more conventional key bindings: `C-t' creates a new tab, `C-w' closes the current one, and `C-r' runs the definitions. On Mac OS X, the Command key is used. See "Defining Custom Shortcuts" in the DrRacket manual for an example that uses the old key bindings. * The new `raco link' command registers a directory as a collection, which allows the collection directory to reside outside the "collects" tree and without changing the PLTCOLLECTS environment variable. * Typed Racket: - Typed Racket provides static performance debugging support to show which code gets optimized and point out code that does not. Use the "Performance Report" button in DrRacket. - More intuitive types in printouts in the REPL and in error messages. Use `:query-result-type' to explore types, or `:print-type' for a full printout. - Typed Racket now supports defining function with optional arguments using the same syntax as Racket. * Redex now supports specifying (and testing and automatically typesetting) judgment forms including type systems and SOS-style operational semantics. * Fixed several GUI problems, including problems on Ubuntu 11.10 (GTK+ 3) and 64-bit Mac OS X. * Internal-definition expansion has changed to use `let*' semantics for sequences that contain no back references. This change removes a performance penalty for using internal definitions instead of `let' in common cases, and it only changes the meaning of programs that capture continuations in internal definitions. Internal definitions are now considered preferable in style to `let'. * Support for `begin-for-syntax' has been generalized; modules may now define and export both value bindings and syntax bindings (macros) at phase 1 and higher. Due to a bug, phase 1 syntax (or higher) is not available in DrRacket's `#lang'-based REPL. A simple workaround is to disable debugging in DrRacket (see "no debugging" radio button in detailed language dialog). Additional Items: * The `racket/gui' library (and Slideshow) provides more support for multiple-screen displays. * DrRacket remembers whether an opened file used LF or CRLF line endings, and will continue using the same. When creating a new file, a preference determines how it is saved. * `net/url' can now follow HTTP redirections. * The LNCS and JFP class files are no longer distributed with Racket. Instead, they are downloaded on demand. * The Algol language implementation is now available as a plain language using `#lang algol60'. * The Racket-to-C compiler (as accessed via `raco ctool' or `mzc') has been removed; Racket's JIT has long provided better performance, and the FFI provides better access to C libraries. * Contracts can be applied to exports with the new `contract-out' form within `provide', instead of a separate `provide/contract' form. (The new `contract-out' form is implemented as a new kind of "provide pre-transformer".) * The `date*' structure type is an extension of `date' with `nanosecond' and `time-zone-name' fields. * New looping constructs: `for/sum' and `for/product'. * Direct calls to keyword-accepting functions are now optimized to eliminate the overhead of keywords. In addition, the compiler detects and logs warnings for keyword-argument mismatches. * The libfit interface is available from `plot/deprecated/fit', and will be removed in the near future. * The Unix installer has been re-done, and it is now more robust. * The built-in reader and printer support for Honu is removed. (This functionality is re-implemented in Racket.) On-line Check Syntax: DrRacket now provides an on-line version of the syntax check tool, which means that syntax checking runs automatically while you continue to edit a program. With this tool enabled, its annotations (e.g., binding arrows) and actions (e.g., the renaming refactoring and direct documentation links) are almost always available. We have noticed that on-line syntax checking renders DrRacket unstable on occasion, perhaps because it relies on relatively new support for parallelism. Occurrences of the problem are rare, but they are not rare enough, which is why we have disabled the tool by default. At the same time, current users of the tool find it so valuable that we felt it should be included in the release. We expect to track down the remaining problems and enable the tool by default in near-future release. To enable on-line syntax checking (for `#lang'-based programs only), click on the red dot in the bottom right of DrRacket's window. To turn it off, click there again. -
v5.1.3
76809b92 · ·Racket v5.1.3 This is a bugfix release, resolving the DrRacket issue with the contour view. In addition, two tex files with problematic licensing were removed.
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v5.1.2
9bd8e67e · ·Racket v5.1.2 * The download page includes 64-bit installers for Mac OS X, Windows, and two Debian flavors. Racket now supports OS X Lion. * Racket now includes a new `racket/place' library to support parallelism, complementing `racket/future'. Racket's parallel build process is now based on places instead of multiple OS processes. Places support share-nothing parallelism and message-passing communication. Compared to futures, places are heavyweight, but they have a simpler performance model. * The syntax-certificate system has been replaced by a syntax-taint system. Both certificates and taints were designed to protect otherwise inaccessible bindings from abuse when they appear in macro expansions. Taints are simpler and lighter, and the switch closes known holes in the certificate system. Macros that are not implemented with `syntax-rules' or `define-syntax-rule', however, must explicitly use `syntax-protect' to protect their expansions from abuse. * The `net/url' library supports HTTPS connections, but beware that by default all sites are accepted (equivalent to ignoring a browser's warnings about untrusted certificates). * Error messages in the student languages use a simplified vocabulary and consistent phrasings. If you maintain curriculum material or teachpacks then please consider updating. See the "Error Message Composition Guidelines" section in the documentation for details. * Typed Racket: almost all core Racket data structures and operations are now accessible in Typed Racket (most of this work is due to prolific contributor Eric Dobson). The performance of the typechecker has been significantly improved. * The `scriblib/bibtex' library supports BibTeX-formatted citation databases in Scribble documents. BibTeX can be tricky to parse, so please report failed entries as bug reports. * The `for' forms now support an `#:unless' clause, and a nonnegative integer can be used as a sequence. The new `compose1' function creates single-valued composition functions. The `racket/function' library now provides `identity', `thunk', and `thunk*'. * The license has been clarified: we now use LGPLv2.1 uniformly. (The license file used to specify LGPLv2, contrary to the download pages.)
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v5.1.1
6f8817d0 · ·Racket v5.1.1 * The new `racket/stream' library provides `stream-first', `stream-rest', a lazy `stream-cons', and so on. Streams are a subtype of sequences, so they work in `for' forms. Some sequence generators, such as `in-range', now produce streams. A `racket/sequence' library replaces the old `racket/stream' library. * The new `racket/syntax' library contains facilities useful for writing macros. The new `syntax/srcloc' and `syntax/location' libraries provide support for manipulating source locations. * The `racket/gui' library now supports multi-column list boxes and scrolling panels. * The new `ffi/file' library is useful for writing foreign library bindings that cooperate with Racket's security guard mechanism. * Generators from the `racket/generator' library can now have formal arguments that are used when the generator is fired up. * Single-precision floating-point support is now enabled by default. Single-precision floats print differently from their default double-precision counterparts, new primitives convert between the two precisions, and new reader syntax supports single-precision literals. * JIT improvements include a small change to aid x86 branch prediction on function-call returns, which can speed up some programs significantly. * Typed Racket: - The numeric tower has been entirely overhauled. TR programs can now use more precise types than before, and check more numeric properties, such as sign or range properties. - Fixnum optimizations have been improved and should apply more broadly. - The performance of the typechecker has been improved. In particular, dispatch on large union types should typecheck much faster than before. * The Stepper can now step through Lazy Racket programs. * The `racket/future' library includes `fsemaphore' values, the `future' primitive no longer freezes futures (so a future can spawn new futures), and `future' log messages are more informative. * PLaneT development links are now version-specific. * The `2htdp/image' library now includes `overlay/align', `underlay/align', `overlay/align/offset' and `underlay/align/offset'. * The network protocol for universes in `2htdp/universe' has changed, so that v5.1.1 is incompatible with earlier versions. * The "DrScheme" application (which simply ran DrRacket in the last few releases) has been removed. The "MrEd" GUI executables for Windows and Mac OS X have also been removed, although the "mred" console executable remains for Unix and Mac OS X to support old scripts. -
v5.1
bee619f0 · ·Racket v5.1 The most significant change in version 5.1 is a rewrite of the GUI library: http://blog.racket-lang.org/2010/12/racket-version-5.html Unix/X users will see the biggest difference with this change, because DrRacket and all Racket GUI programs now take on the desktop theme for menus, buttons, and other GUI widgets. In the long run, Racket GUI programs on all platforms will improve as a result of the library rewrite. In the short run, beware that this first release of a new library will inevitably include a new set of bugs. Version 5.1 changes in more detail: * The `racket/draw' library -- which implements the drawing half the GUI toolkit -- can be used independent of the `racket/gui/base' library and without a graphics display (e.g., without an X11 connection). The new library has one small incompatibility with the old GUI toolbox: 'xor drawing is no longer supported. The new library has many additional features: rotation and general affine transformations, PDF and SVG drawing contexts, gradients, and alpha-channel bitmaps. * The GRacket executable is no longer strictly necessary for running GUI programs, because the `racket/gui/base' library can be used from Racket. To the degree that a platform distinguishes GUI and console applications, however, the GRacket executable still offers some additional GUI-specific functionality (e.g., single-instance support). The new `racket/gui/base' library includes small incompatibilities with the old GUI toolbox: the `send-event', `current-ps-afm-file-paths', and `current-ps-cmap-file-paths' functions have been removed. The `racket/gui/base' library re-exports `racket/draw', so it includes the same drawing functionality as before (except for 'xor drawing). * The new `racket/snip' library can be used independently of `racket/gui/base' to work with graphical editor content (e.g., images in student programs). Like `racket/draw', the `racket/snip' library is re-exported by `racket/gui/base'. * The Web Server includes a backwards incompatible change that prevents X-expressions and lists of bytes from being directly returned from servlets. This change will increase performance for those types of responses and allow easier experimentation with response types. Please see "collects/web-server/compat/0/README" in the installation to learn about porting your servlets forward. Don't worry. It's easy. * The new `raco demodularize' tool collapses a module's dependencies into a single module comprising the whole program. This transformation currently provides no performance improvement, but is the basis for cross-module optimization and dead-code elimination tools to come. The transformation is currently useful for static analysis of whole Racket programs. * The picturing-programs teachpack, formerly installed via PLaneT, is now bundled with the standard distribution. Use the teachpack with `(require picturing-programs)' instead of `(require installed-teachpacks/picturing-programs)'. The old PLaneT-based installation procedure still works, but it now merely installs a stub that invokes the bundled version. * Slideshow picts, `racket/draw' bitmaps, and images created with `2htdp/image' can now be used directly in Scribble documents. More generally, the new `file/convertible' protocol enables any value that is convertible to a PNG and/or PDF stream to be used as an image in a Scribble document. * The Same game sports a new look and an improved scoring system. (The current known high score is 12,429; can you beat that?)
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v5.0.2
371b00af · ·Racket v5.0.2 * Typed Racket's optimizer is now turned on by default; error messages have been simplified and clarified. * Contracts: contracts on mutable containers allow functions or other higher order values, and contracts are checked when updating or dereferencing the containers. The new contracts are slower than the old ones, so the old check-once functionality is still available. A new dependent function contract combinator, `->i', properly assigns blame for contracts that violate themselves and the generated wrappers are more efficient than `->d'. (Although it does more checking so your contracts may be faster or slower). See the docs for `box/c', `hash/c', `vector/c', `vectorof' and `->i' for more details. * The `when', `unless', `cond', `case', and `match' forms (in `racket/base' and derived languages) now allow immediate internal definitions. * Web server: the formlets library provides more HTML form elements; `make-xexpr-response' supports a preamble for DTD declarations; `serve/servlet' supports stateless servlets. * New WebSocket implementation, see `net/websocket' for details. * The new `data' collection contains implementations of several data structures, including growable vectors and order-based dictionaries. * `racket/match' is now significantly faster * The Racket documentations are built in parallel by default. * The stepper is now compatible with programs using the Universe teachpack. * `2htdp/image': pinholes are now supported in the library (if you don't use pinhole primitives you will not see them); a number of new triangle functions added; supports conversion of images to color lists and back. Also, cropping has been improved for scenes; see the documentation section on the nitty-gritty of pixels for details. * Signatures have been moved to ASL, BSL, BSL+, ISL, and ISL+ (HtDP teaching languages) no longer support checked signatures. * Student languages: one-armed `check-error' in all levels; ASL is extended with hash operations, and `define-datatype'. * DMdA languages: Checking for parametric signatures is now eager. This catches errors earlier, but retains the asymptotic complexity properties; signatures for record types now have generators; `list-of' and `any' signatures are now provided.
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v5.0.1
2c77ae5e · ·Racket v5.0.1 * Datalog is a lightweight deductive database system with Racket integration. It is now available in the `datalog' collection and with `#lang datalog'. * Racklog provides Prolog-style logic programming in Racket, adapted from Dorai Sitaram's Schelog package. It is available in the `racklog' collection and now as `#lang racklog'. * By default `make install' and `raco setup' compile collections in parallel on all available processors. (Use `raco setup -j 1' to disable, if necessary.) * Changes (as part of 5.0) in the `racket' language compared to the `scheme' language: constructor-style printing, a `struct' alternative to `define-struct' that fits more naturally with `match' and constructor-style printing, bytecode-dependency management via SHA-1 hashes instead of just timestamps (where the `openssl/sha1' library provides the SHA-1 hash function), a reorganization of `scheme/foreign' into `ffi/unsafe' and associated libraries, and new printing functions `eprintf' and `displayln'. Also, a generator from `racket/generator' is required to have the form `(generator () body ...)', which supports a planned extension to let a generator accept arguments. * Changes to the `racket' language (since 5.0): internal-definition positions allow mixing expressions with definitions, full continuations can escape past a continuation barrier, custodians can attempt to terminate subprocesses and subprocess groups (see `current-subprocess-custodian-mode', `subprocess-group-enabled'), the JIT supports additional unboxing flonum operations and unsafe variants, `ffi/unsafe' provides an asychronous-call mechanism to deal with foreign threads, a new "." modifier for format string directives (e.g., "~.s" and "~.a") limits the respective output to `(error-print-width)' characters. * The core type system of Typed Racket has been substantially revised. In particular, Typed Racket can now follow significantly more sophisticated reasoning about the relationships between predicates. Additionally, Typed Racket now allows variable arity types in more places, allowing programmers to specify variable-arity lists. * We are working on an optimizing version of Typed Racket that takes advantage of type information for certain classes of programs. This project is a work in progress. For those interested, see the documentation for `#:optimized'. * The `web-server/formlets' library adds a `formlet*' form that allows dynamic formlet construction, as opposed to `formlet' which requires syntactic Xexprs and static formlets. Several new library formlets are added. * The `syntax/parse' library has new support for matching literals at different phases using the `#:phase' argument for literals and literal sets. * RackUnit now includes a GUI test runner as `rackunit/gui'. * The `2htdp/image' library now includes `flip-vertical' and `flip-horizontal' operations that mirror images (vertically and horizontally).
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v5.0
0954877d · ·PLT is happy to announce the release of Racket, available from http://racket-lang.org/ With Racket, you can script command shells and web servers; you can quickly prototype animations and complex GUIs; regexps and threads are here to serve you. To organize your systems, you can mix and match classes, modules or components. Best of all, you start without writing down types. If you later wish to turn your script into a program, equip your Racket modules with explicit type declarations as you wish. And Racket doesn't just come as a typed variant; you can also write your modules in a purely functional and lazy dialect. Racket comes in so many flavors because Racket is much more than a standard scripting language or a plain programming language. Racket supports language extensibility to an unequaled degree. A Racket programmer knows that making up a new language is as easy as writing a new library. To help you start quickly, Racket includes batteries in all shapes and sizes, most importantly, extensive documentation and all kinds of libraries. Racket occupies a unique position between research and practice. It inherits many major ideas from language research, among them type safety (when the type system says that x is a number, then at runtime it always is a number) and memory safety (when some memory is reclaimed by the garbage collector it is impossible to still have a reference to it). At the same time, user demand governs rigid adherence to purely theoretical principles. Racket, formerly PLT Scheme, is a product of over 15 years of development. Although Racket starts with a mature software base and an established user community, its new name reflects our view that this is just the beginning of Racket's evolution.
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