(source-fn x)
Returns a string of the source code for the given symbol, if it can find it. This requires that the symbol resolve to a Var defined in a namespace for which the .clj is in the classpath. Returns nil if it can't find the source. For most REPL usage, 'source' is more convenient. Example: (source-fn 'filter)
(source-fn 'max)
;;=> "(defn max
\\"Returns the greatest of the nums.\\"
{:added \\"1.0\\"
:inline-arities >1?
:inline (nary-inline 'max)}
([x] x)
([x y] (. clojure.lang.Numbers (max x y)))
([x y & more]
(reduce1 max (max x y) more)))"