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Does Clojure follow the Common Lisp standard?

I recently found out that I can use any dialect of Lisp for the functional programming course at school, if it follows the Common Lisp standard. Does Clojure follow this standard? Is it too different?

Solution

  • Clojure does not follow the Common Lisp standard - it is an entirely new Lisp.

    That being said, it shares a lot of thing with Common Lisp so knowledge gained in one will be generally applicable to the other.

    Many key things are the same:

    • Function application by putting a function at the beginning of a list followed by its arguments: (my-function arg1 arg2)
    • "Code is data" - code is expressed in homoiconic forms that are also Lisp data structures
    • Both have a powerful macro system - you can write functions to generate arbitrary code
    • They are dynamic languages,
    • Both emphasise interactive development using a REPL
    • They are both normally compiled

    Some things that are different:

    • Clojure has a stronger emphasis on functional programming - all the data structures are immutable and the core library is composed mainly of "pure" functions. Note: you can still use a functional style in Common Lisp, Clojure just puts it more at the forefront
    • Clojure is a Lisp-1 (like Scheme functions and data share the same namespace) whereas Common Lisp is a Lisp-2 (functions and data have a different namespace)
    • Clojure has new literals for maps {}, vectors [] and sets #{} in addition to the traditional Lisp lists ()
    • Common Lisp supports reader macros - which gives you greater ability to customise the syntax of the language
    • Clojure has a novel approach to managing concurrency, identity and state via STM - see http://www.infoq.com/presentations/Value-Identity-State-Rich-Hickey
    • Clojure is designed to "embrace the host platform" (usually the JVM, but also the CLR and recently there has been a lot of interest in targeting JavaScript via ClojureScript) - this is important from a practical perspective as it gives you access to a huge array of libraries / tools.
    • There is no Clojure standard - its a BDFL driven language with one primary open source implementation. It helps enormously that Rich Hickey is the BDFL - the guy is a genius.

    Subjective opinion: I'm biased but I think that for most modern usage Clojure is definitely the way to go if you are choosing a Lisp nowadays - it's a modern redesign of Lisp, has a very vibrant and innovative community, is a pragmatic choice for "getting things done".