Why Not a Function #20: add-leading-zeros

(defn add-leading-zeros
  [n s]
  (str/replace s #"\d+"
    #(str/join (concat (repeat (- n (count %)) "0") [%]))))

add-leading-zeros prepends numbers in the string with the 0 characters until each of the numbers reaches the desired length. It can be used, for example, for intelligent sorting.

(add-leading-zeros 3 "line 1: it's #wnaf #20! ")
=> "line 001: it's #wnaf #020! "

Written on April 7, 2020