| Clojure | |
|---|---|
 | |
| Paradigm | multi-paradigm: |
| Family | Lisp |
| Designed by | Rich Hickey |
| First appeared | 2007; 18 years ago (2007) |
| Stable release | |
| Typing discipline | |
| Memory management | Garbage collection via a host (JVM,CLR, aJavaScript runtime such asV8 in case of ClojureScript orBEAM (seebelow) |
| Platform | |
| License | Eclipse Public |
| Filename extensions |
|
| Website | clojure |
| Dialects | |
| ClojureScript, ClojureDart | |
| Influenced by | |
| Influenced | |
| |
Clojure (/ˈkloʊʒər/, likeclosure)[17][18] is adynamic andfunctionaldialect of theprogramming languageLisp on theJava platform.[19][20]
Like most other Lisps, Clojure'ssyntax is built onS-expressions that are firstparsed intodata structures by aLisp reader before beingcompiled.[21][17] Clojure's reader supports literal syntax formaps, sets, andvectors along with lists, and these are compiled to the mentioned structures directly.[21] Clojure treatscode as data and has aLisp macro system.[22] Clojure is aLisp-1 and is not intended to be code-compatible with other dialects of Lisp, since it uses its own set of data structures incompatible with other Lisps.[22]
Clojure advocatesimmutability andimmutable data structures and encourages programmers to be explicit about managing identity and its states.[23] This focus on programming with immutable values and explicit progression-of-time constructs is intended to facilitate developing more robust, especiallyconcurrent, programs that are simple and fast.[24][25][17] While its type system is entirelydynamic, recent efforts have also sought the implementation of adependent type system.[26]
The language was created byRich Hickey in the mid-2000s, originally for the Java platform; the language has since been ported to other platforms, such as theCommon Language Runtime (.NET). Hickey continues to lead development of the language as itsbenevolent dictator for life.
Rich Hickey is the creator of the Clojure language.[19] Before Clojure, he developeddotLisp, a similar project based on the.NET platform,[27] and three earlier attempts to provide interoperability between Lisp andJava: aJava foreign language interface forCommon Lisp (jfli),[28] AForeign Object Interface for Lisp (FOIL),[29] and aLisp-friendly interface to Java Servlets (Lisplets).[30]
Hickey spent about two and a half years working on Clojure before releasing it publicly in October 2007,[31] much of that time working exclusively on Clojure with no outside funding. At the end of this time, Hickey sent an email announcing the language to some friends in the Common Lisp community.
Clojure's name, according to Hickey, is aword play on the programming concept "closure" incorporating the letters C, L, and J forC#,Lisp, andJava respectively—three languages which had a major influence on Clojure's design.[18]
Rich Hickey developed Clojure because he wanted a modernLisp forfunctional programming, symbiotic with the establishedJava platform, and designed forconcurrency.[24][25][32][17] He has also stressed the importance of simplicity in programming language design and software architecture, advocating forloose coupling,polymorphism viaprotocols and type classes instead ofinheritance,stateless functions that arenamespaced instead ofmethods orreplacing syntax with data.[33][34][35]
Clojure's approach tostate is characterized by the concept of identities,[23] which are represented as a series of immutable states over time. Since states are immutable values, any number of workers can operate on them in parallel, and concurrency becomes a question of managing changes from one state to another. For this purpose, Clojure provides several mutablereference types, each having well-defined semantics for the transition between states.[23]
Clojure runs on the Java platform and as a result, integrates with Java and fully supports calling Java code from Clojure,[36][17] and Clojure code can be called from Java, too.[37] The community uses tools such as Clojurecommand-line interface (CLI)[38] orLeiningen for project automation, providing support forMaven integration. These tools handle project package management and dependencies and are configured using Clojure syntax.
As a Lisp dialect, Clojure supportsfunctions asfirst-class objects, aread–eval–print loop (REPL), and a macro system.[6] Clojure'sLisp macro system is very similar to that ofCommon Lisp with the exception that Clojure's version of thebackquote (termed "syntax quote") qualifies symbols with theirnamespace. This helps prevent unintended name capture, as binding to namespace-qualified names is forbidden. It is possible to force a capturing macro expansion, but it must be done explicitly. Clojure does not allow user-defined reader macros, but the reader supports a more constrained form of syntactic extension.[39] Clojure supportsmultimethods[40] and forinterface-like abstractions has aprotocol[41] based polymorphism and data type system usingrecords,[42] providing high-performance and dynamic polymorphism designed to avoid theexpression problem.
Clojure has support forlazy sequences and encourages the principle ofimmutability andpersistent data structures. As afunctional language, emphasis is placed onrecursion andhigher-order functions instead of side-effect-based looping. Automatictail call optimization is not supported as the JVM does not support it natively;[43][44][45] it is possible to do so explicitly by using therecur keyword.[46] Forparallel andconcurrent programming Clojure providessoftware transactional memory,[47] a reactiveagent system,[1] andchannel-based concurrent programming.[48]
Clojure 1.7 introduced reader conditionals by allowing the embedding of Clojure, ClojureScript and ClojureCLR code in the same namespace.[49][21] Transducers were added as a method for composing transformations. Transducers enable higher-order functions such asmap andfold to generalize over any source of input data. While traditionally these functions operate onsequences, transducers allow them to work on channels and let the user define their own models for transduction.[50][51][52]
Extensible Data Notation, oredn,[53] is a subset of the Clojure language intended as a data transfer format. It can be used to serialize and deserialize Clojure data structures, and Clojure itself uses a superset of edn to represent programs.
edn is used in a similar way toJSON orXML, but has a relatively large list of built-in elements, shown here with examples:
true,false"foo bar"\c,\tabname:key1233.14(a b 42)[a b 42]{:a 1, "foo" :bar, [1 2 3] four}#{a b [1 2 3]}nil (anull-like value)In addition to those elements, it supports extensibility through the use oftags, which consist of the character# followed by a symbol. When encountering a tag, the reader passes the value of the next element to the corresponding handler, which returns a data value. For example, this could be a tagged element:#myapp/Person {:first "Fred" :last "Mertz"}, whose interpretation will depend on the appropriate handler of the reader.
This definition of extension elements in terms of the others avoids relying on either convention or context to convey elements not included in the base set.
The primary platform of Clojure isJava,[20][36] but other target implementations exist. The most notable of these is ClojureScript,[54] which compiles toECMAScript 3,[55] and ClojureCLR,[56] a full port on the.NET platform, interoperable with its ecosystem.
Other implementations of Clojure on different platforms include:
Tooling for Clojure development has seen significant improvement over the years. The following is a list of some popularIDEs andtext editors with plug-ins that add support for programming in Clojure:[65]
In addition to the tools provided by the community, the official Clojurecommand-line interface (CLI) tools[38] have also become available onLinux,macOS, andWindows since Clojure 1.9.[78]
The development process is restricted to the Clojure core team, though issues are publicly visible at the ClojureJIRA project page.[79] Anyone can ask questions or submit issues and ideas at ask.clojure.org.[80] If it's determined that a new issue warrants a JIRA ticket, a core team member will triage it and add it. JIRA issues are processed by a team of screeners and finally approved by Rich Hickey.[81][82]
With continued interest in functional programming, Clojure's adoption by software developers using the Java platform has continued to increase.[83] The language has also been recommended by software developers such as Brian Goetz,[84][85][86] Eric Evans,[87][88]James Gosling,[89]Paul Graham,[90] andRobert C. Martin.[91][92][93][94]ThoughtWorks, while assessing functional programming languages for their Technology Radar,[95] described Clojure as "a simple, elegant implementation of Lisp on the JVM" in 2010 and promoted its status to "ADOPT" in 2012.[96]
In the "JVM Ecosystem Report 2018" (which was claimed to be "the largest survey ever of Java developers"), that was prepared in collaboration by Snyk and Java Magazine, ranked Clojure as the 2nd most used programming language on the JVM for "main applications".[97] Clojure is used in industry by firms[98] such asApple,[99][100]Atlassian,[101]Funding Circle,[102]Netflix,[103]Nubank,[104]Puppet,[105] andWalmart[106] as well as government agencies such asNASA.[107] It has also been used for creative computing, including visual art, music, games, and poetry.[108]
In the 2023 edition ofStack Overflow Developer Survey, Clojure was the fourth mostadmired in the category of programming and scripting languages, with 68.51% of the respondents who have worked with it last year saying they would like to continue using it. In thedesired category, however it was marked as such by only 2.2% of the surveyed, whereas the highest scoringJavaScript wasdesired by 40.15% of the developers participating in the survey.[109]
| Version | Release date | Major features, improvements |
|---|---|---|
| October 17, 2007 (2007-10-17)[31] | Initial public release | |
| 1.0 | May 4, 2009 (2009-05-04)[110] | First stable release |
| 1.1 | December 31, 2009 (2009-12-31)[111] | Futures |
| 1.2 | August 19, 2010 (2010-08-19)[112] | Protocols |
| 1.3 | September 23, 2011 (2011-09-23)[113] | Enhanced primitive support |
| 1.4 | April 15, 2012 (2012-04-15)[114] | Reader literals |
| 1.5 | March 1, 2013 (2013-03-01)[115] | Reducers |
| 1.5.1 | March 10, 2013 (2013-03-10)[116] | Fixing a memory leak |
| 1.6 | March 25, 2014 (2014-03-25)[117] | Java API, improved hashing algorithms |
| 1.7 | June 30, 2015 (2015-06-30)[49] | Transducers, reader conditionals |
| 1.8 | January 19, 2016 (2016-01-19)[118] | Additional string functions, direct linking, socket server |
| 1.9 | December 8, 2017 (2017-12-08)[119] | Integration with spec, command-line tools |
| 1.10 | December 17, 2018 (2018-12-17)[120] | Improved error reporting, Java compatibility |
| 1.10.1 | June 6, 2019 (2019-06-06)[121] | Working around a Java performance regression and improving error reporting fromclojure.main |
| 1.10.2 | January 26, 2021 (2021-01-26)[122] | Java interoperability/compatibility improvements and other important language fixes |
| 1.10.3 | March 4, 2021 (2021-03-04)[123] | prepl support for reader conditionals |
| 1.11.0 | March 22, 2022 (2022-03-22)[124] | New syntax for keyword argument invocation, newclojure.math namespace, namespace aliasing without loading, and new helper functions added toclojure.core |
| 1.11.1 | April 5, 2022 (2022-04-05)[125] | Rolling back unintended change in binary serialisation of objects of typesclojure.lang.Keyword andclojure.lang.ArraySeq. |
| 1.11.2 | March 8, 2024 (2024-03-08)[126] | Fix forCVE-2024-22871Denial of Service |
| 1.12.0 | September 5, 2024 (2024-09-05)[127] | Java method values, params type hints, array class syntax,add-lib,clojure.java.process |
| 1.12.1 | June 2, 2025 (2025-06-02)[128] | Includes bug fixes, improved interop, enhanced tool support, and metadata updates. |
| 1.12.2 | August 25, 2025 (2025-08-25)[129] | Fixes for CLJ-2914, CLJ-1798, CLJ-2916 and CLJ-2917. |
| Latest version:1.12.3 | August 25, 2025 (2025-08-25)[8] | Fix for CLJ-2919. |
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