How can I display the definition of a function in Clojure at the REPL?

Question

I'm looking for the ability to have the REPL print the current definition of a function. Is there any way to do this?

For example, given:

(defn foo [] (if true "true")) 

I'd like to say something like

(print-definition foo) 

and get something along the lines of

(foo [] (if true "true")) 

printed.

Answer 1

An alternative to source (which should be available via clojure.repl/source when starting a REPL, as of 1.2.0. If you're working with 1.1.0 or lower, source is in clojure.contrib.repl-utils.), for REPL use, instead of looking at functions defined in a .clj file:

(defmacro defsource   "Similar to clojure.core/defn, but saves the function's definition in the var's    :source meta-data."   {:arglists (:arglists (meta (var defn)))}   [fn-name & defn-stuff]   `(do (defn ~fn-name ~@defn-stuff)        (alter-meta! (var ~fn-name) assoc :source (quote ~&form))        (var ~fn-name)))  (defsource foo [a b] (+ a b))  (:source (meta #'foo)) ;; => (defsource foo [a b] (+ a b)) 

A simple print-definition:

(defn print-definition [v]   (:source (meta v)))  (print-definition #'foo) 

#' is just a reader macro, expanding from #'foo to (var foo):

(macroexpand '#'reduce) ;; => (var reduce)