Start the REPL by typing lein repl. You are automatically placed into the user namespace.
Using the hello-world function from the previous chapter in the REPL would look like this:
hello-world takes no arguments and returns the string "Hello, World".
user> (hello-world)
"Hello, World"
If you forget the ( ) around the function name, you'll see something like this:
user> hello-world
\#object[user$hello_world 0xf388310 "user$hello_world@f388310"]
You can see the docs and parameters for a function by calling doc.
user> (clojure.repl/doc hello-world)
-------------------------
user/hello-world
([])
ye olde 'Hello, World'
You can do (doc hello-world) if you have the clojure.repl namespace already loaded.
You can look up any function in Clojure! Here is a couple:
user> (doc clojure.string/join)
-------------------------
clojure.string/join
([coll] [separator coll])
Returns a string of all elements in coll, as returned by (seq coll),
separated by an optional separator.
user=> (doc first)
-------------------------
clojure.core/first
([coll])
Returns the first item in the collection. Calls seq on its
argument. If coll is nil, returns nil.