Question

I am wondering what the differences — if any — in the argument vectors of the following two functions. I believe I understand what is going on intuitively, but the first one caught me off guard. Thank you.

From Stackoverflow recursion in clojure

(defn foo
  ([x] (foo x []))
  ([x current]
     (if (= x 0)
       (apply vector (sort < current))
       (recur (dec x) (conj current x)))))

and one of my own functions

(defn strip-csv-header
    "Pulls out first row from csv data. If column definitions, those will
     be removed; else first row of data will be removed."

    [csv-data-all]
    (let [csv-data (rest csv-data-all)]
        csv-data))

Answer 1

foo works with either one or two parameters wherein strip-csv-header will only function with one parameter.

(defn foo
  ([x] (foo x [])) ; one arg path

  ([x current]     ; two args path
     (if (= x 0)
       (apply vector (sort < current))
       (recur (dec x) (conj current x)))))