Clojure REPL docs
In this post we show how to read docs in Clojure REPL. You’ll learn useful commands to find and display Clojure and Java docs, how to display Clojure source code.
Print documentation
To print documentation of a function, var, namespace, macro, etc. just use the doc macro - (doc var\_or\_special\_form):
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user> (doc doc)
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clojure.repl/doc
([name])
Macro
Prints documentation for a var or special form given its name
user> (doc clojure.repl)
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clojure.repl
Utilities meant to be used interactively at the REPL
Find docs matching patterns
To find any documentation by regexp use (find-doc "RegExp"):
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user> (find-doc "red.cer")
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clojure.core.reducers/->Cat
([cnt left right])
Positional factory function for class clojure.core.reducers.Cat.
-------------------------
clojure.core.reducers/reducer
([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.
-------------------------
clojure.core.reducers
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):
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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):
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;; 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.
However, if you would like to display Javadoc locally you will need to add its location:
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;; Add local doc path if you have:
user> (clojure.java.javadoc/add-local-javadoc "/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 because a 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 get an exception:
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myns> (doc clojure.repl/apropos)
CompilerException java.lang.RuntimeException: Unable to resolve symbol: doc in this context, compiling:(*cider-repl localhost*:134:16)
To fix that you have to import the functions by yourself:
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myns> (use '[clojure.repl :only (dir doc find-doc source)])
myns> (doc clojure.repl/apropos)
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clojure.repl/apropos
([str-or-pattern])
Given a regular expression or stringable thing, return a seq of all
public definitions in all currently-loaded namespaces that match the
str-or-pattern.
Inject repl tools automatically
If you are using Leiningen then you can inject helper functions automatically from your ~/.lein/profiles.clj file:
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{:repl {:injections [(use '[clojure.repl :only [doc find-doc source]])]}}
References:
- Check out other parts of Clojure Tutorial!
- Clojure reference