Skip to content

Latest commit

 

History

History
69 lines (52 loc) · 2.18 KB

bare-bones.asciidoc

File metadata and controls

69 lines (52 loc) · 2.18 KB

Bare-Bones Clojure

by John Cromartie

Problem

You want to use Clojure but you don’t want to install additional tools.

Solution

Obtain the Clojure JAR file by downloading and unzipping a release from http://clojure.org/downloads. Using a terminal, navigate to where you extracted the JAR, and start a Clojure REPL.

$ java -cp "clojure-1.5.1.jar" clojure.main

You are now running an interactive Clojure REPL (Read-Eval-Print Loop). Type an expression and hit <Enter> to evaluate it. Press <Ctrl>+D to exit.

Discussion

The fact that Clojure on the JVM is encapsulated in a simple JAR file has some great benefits. For one, it means that Clojure is never really installed. It’s just a dependency like any other Java library. You can easily swap out one version of Clojure for another by replacing a single file.

Let’s dissect the java invocation here a bit.

-cp "clojure-1.5.1.jar"

This sets the Java classpath to include Clojure (and only Clojure, in this example). A full explanation of the classpath is beyond the scope of this recipe, but suffice to say it is a list of places where Java should look to load classes. A full discussion of Classpaths on the JVM can be found at http://docs.oracle.com/javase/tutorial/essential/environment/paths.html

clojure.main

Here we are specifying the class which Java should load and execute the main method. Yes, clojure.main is really a Java class. The reason this doesn’t look like a typical Java invocation is because Clojure namespaces, which are compiled to classes, do not conventionally use capitalized names like Java classes do.

This is the absolute bare-minimum Clojure environment, and is all you need to run Clojure code on any system with Java installed. Of course, for regular use and development, you will most certainly want a more feature-rich solution like Leiningen.

In some cases, however, hand-tuning a Java invocation may be the best way to integrate Clojure into your environment. This is particularly useful on servers where deploying a simple JAR file is trivial compared to installing more complex packages.

See Also

  • Leiningen

  • Running Clojure Programs