What's the easiest way to parse numbers in clojure?

Question

I\'ve been using java to parse numbers, e.g.

(. Integer parseInt  numberString)

Is there a more clojuriffic way that would handle both int

Answer 1

In my opinion the best/safest way that works when you want it to for any number and fails when it isn't a number is this:

(defn parse-number
  "Reads a number from a string. Returns nil if not a number."
  [s]
  (if (re-find #"^-?\d+\.?\d*$" s)
    (read-string s)))

e.g.

(parse-number "43") ;=> 43
(parse-number "72.02") ;=> 72.02
(parse-number "009.0008") ;=> 9.008
(parse-number "-92837482734982347.00789") ;=> -9.2837482734982352E16
(parse-number "89blah") ;=> nil
(parse-number "z29") ;=> nil
(parse-number "(exploit-me)") ;=> nil

Works for ints, floats/doubles, bignums, etc. If you wanted to add support for reading other notations, simply augment the regex.