Programming for fun and profit

Programming tutorials, problems, solutions. Always with code.

Clojure REPL docs

In this post we show how to use look for useful information in Clojure REPL? You’ll learn how to find and display docs, loot at Clojure source code and display Javadocs.

Print documentation

To print documentation of a function, var, namespace, macro, etc. just use the doc macro – (doc var_or_special_form):

user> (doc doc)
  Prints documentation for a var or special form given its name

user> (doc clojure.repl)
  Utilities meant to be used interactively at the REPL

Find docs matching patterns

To any documentation by regexp use (find-doc “RegExp”):

user> (find-doc "red.cer")
([cnt left right])
  Positional factory function for class clojure.core.reducers.Cat.
([coll xf])
  Given a reducible collection, and a transformation function xf,
  returns a reducible collection, where any supplied reducing
  fn will be transformed by xf. xf is a function of reducing fn to
  reducing fn.
  A library for reduction and parallel folding. Alpha and subject
      to change.  Note that fold and its derivatives require Java 7+ or
      Java 6 + jsr166y.jar for fork/join support. See Clojure's pom.xml for the
      dependency info.

Display source

One of the most useful things – (source symbol)

user> (source identity)
(defn identity
  "Returns its argument."
  {:added "1.0"
   :static true}
  [x] x)

Display JavaDoc

To display API docs of Java classes in default browser – (javadoc object-or-class):

;; opens JavaDoc for String class in default browser
user> (javadoc String)

;; The same as above, because `javadoc` will take class
;; of the given object and then proceed in the same way:
user> (javadoc "aoeu")

By default it opens remote Oracle’s JDK page for given class/object.

If you would like to display JavaDoc locally you will need to add its location:

;; Add local doc path if you have:
user> ( "/home/przemek/doc/java/jdk-8-api/api/")

Now (javadoc Thread) will display local page for given class or will fallback to remote site if it won’t find it locally (usually wrong path was defined).

Clojure REPL helpers in other namespaces

When you start Clojure REPL and begin within user namespace you will have the following functions at your disposal: doc, find-doc, source, and javadoc. But when you switch to other namespace and try to use them you will receive an exception:

myns> (doc clojure.repl/apropos)
CompilerException java.lang.RuntimeException: Unable to resolve symbol: doc in this context, compiling:(*cider-repl localhost*:134:16)

You will have to import the functions by yourself:

myns> (use '[clojure.repl :only (dir doc find-doc source)])
myns> (doc clojure.repl/apropos)
  Given a regular expression or stringable thing, return a seq of all
public definitions in all currently-loaded namespaces that match the

Inject repl tools automatically

If you are using Leiningen then you can inject helper functions automatically from your ~/.lein/profiles.clj file:

{:repl {:injections [(use '[clojure.repl :only [doc find-doc source]])]}}


Share with the World!