Project Euler Problem 8 in Clojure

Not very interesting solution, since I use int/string conversions. As a clojure newcomer it feels a bit weird using the Java String API, just because you know its there. Writing functions to wrap the Java String API is probably not idiomatic Clojure, but I think it might be nice to wrap them in macros one day, to make the substring calls look a bit more Clojure-ish.

Solves in about 20msec.

(def bignumber "73167176531330624919......") ;; elided

(defn- calc-offsets []
  (range 0 (- 1000 5)))

(defn- five-digit-list [bigstring offset]
  (let [substr (.substring bigstring offset (+ 5 offset))]
    (map #(Integer/parseInt (str %)) substr)))

(defn- five-digit-lists [bigstring]
  (map #(five-digit-list bigstring %) (calc-offsets)))

(defn solve []
  (apply max (map #(apply * %) (five-digit-lists bignumber))))