Clojure - map with unbound function

Question

I'm following a Clojure tutorial in Try Clojure , where we are introduced to defining our functions -

(defn square [x] (* x x))

Then apply it to a list of numbers:

(map square [1 2 3 4])

Which promptly prints out an error: java.lang.IllegalStateException: Attempting to call unbound fn: #'sandbox14750/square

When I try to map for example function inc , that works fine - what's the difference between the built-in function inc and my square ?

Answer 1

I had some trouble the first time I tried to run it though after refreshing the page it went fine.

Give me some Clojure:
> (defn square [x] (* x x))
#'sandbox6361/square
> (square 4)
16
> (map square [1 2 3 4])
(1 4 9 16)

If you want to make sure your functions are still available when you need them you can store your functions in locals instead of vars like so:

> (let [square (fn [x] (* x x))] (map square [1 2 3 4]))
(1 4 9 16)
>  

many sandbpxed environments like Clojurebot on #clojure don't let you define arbitrary state so it's worth knowing that functions can be stored in many ways, not just in vars.