In Clojure how can I convert a String to a number?

Question

I have various strings, some like \"45\", some like \"45px\". How how I convert both of these to the number 45?

Answer 1

This isn't perfect, but here's something with filter, Character/isDigit and Integer/parseInt. It won't work for floating point numbers and it fails if there is no digit in the input, so you should probably clean it up. I hope there's a nicer way of doing this that doesn't involve so much Java.

user=> (defn strToInt [x] (Integer/parseInt (apply str (filter #(Character/isDigit %) x))))
#'user/strToInt
user=> (strToInt "45px")
45
user=> (strToInt "45")
45
user=> (strToInt "a")
java.lang.NumberFormatException: For input string: "" (NO_SOURCE_FILE:0)