Portuguese NIF Validator made with Clojure

clojure-portuguese-nif-validator

(defn in?
  "Evaluate true if collection contains element."
  [coll elem]
  (some #(= elem %) coll))

(defn str->int
  "Transform string with number into vector of ints."
  [nif-vector]
  (mapv #(Integer/parseInt %) (map str nif-vector)))

(defn calculate-control-number
  "Multiply each number and sum it."
  [fiscal-number]
  (reduce + (mapv * (butlast fiscal-number) [9 8 7 6 5 4 3 2])))

(defn fiscal-modulo
  "Calculate modulo control number."
  [control-number]
  (- control-number (* (int (/ control-number 11)) 11)))

(defn fiscal-number-validator
  "Takes a string of fiscal number ex.:'`589102392`' and checks if it is
  a valid Portuguese Fiscal Number.
  Returns `true` if valid and `nil` if invalid."
  [nif]
  (let [fiscal-number (str->int nif)]
    (if (= 9 (count fiscal-number))
      (if (or (in? [1 2 5 6 8 9] (first fiscal-number))
               (some true? (map #(= (vec (first fiscal-number) (second fiscal-number))))))
        (let
            [control-number (calculate-control-number fiscal-number)
             modulo (fiscal-modulo control-number)]
          (if (or (= modulo 0) (= modulo 1))
            (= (last fiscal-number) 0)
            (= (last fiscal-number) (- 11 modulo))))))))

(fiscal-number-validator "505795663")
; => true

(fiscal-number-validator "525795663")
; => false

(fiscal-number-validator "862585236")
; => true