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

You can use the edn reader to parse numbers. This has the benefit of giving you floats or Bignums when needed, too.

user> (require '[clojure.edn :as edn])
nil
user> (edn/read-string "0.002")
0.0020

If you want one huge vector of numbers, you could cheat and do this:

user> (let [input "5  10  0.002\n4  12  0.003"]
        (read-string (str "[" input "]")))
[5 10 0.0020 4 12 0.0030]

Kind of hacky though. Or there’s re-seq:

user> (let [input "5  10  0.002\n4  12  0.003"]
        (map read-string (re-seq #"[\d.]+" input)))
(5 10 0.0020 4 12 0.0030)

Or one vector per line:

user> (let [input "5  10  0.002\n4  12  0.003"]
        (for [line (line-seq (java.io.BufferedReader.
                              (java.io.StringReader. input)))]
             (vec (map read-string (re-seq #"[\d.]+" line)))))
([5 10 0.0020] [4 12 0.0030])

I’m sure there are other ways.