Primes and Palidromes

prime_days.clj

(ns prime-days
  (:require [clj-time.core :as t]
            [clj-time.format :as f]
            [clojure.pprint :refer [pprint]]))

(defn prime? [n]
  (.isProbablePrime (BigInteger/valueOf n) 1))

(defn formatted-date [n]
  (f/unparse
   (f/formatters :basic-date)
   n))

(defn date-time->num
  [n]
  (Integer/valueOf (formatted-date n)))

(defn prime-date? [d]
  (prime? (date-time->num d)))

(defn palindrome-date? [d]
  (let [f-date (f/unparse (f/formatter "MdYY") d)]
    (= f-date (clojure.string/reverse f-date))))

(defn get-all-days [pred? year]
  (loop [d (t/now)
         prime-days '() ]
    (if (not (t/after? d (t/plus (t/now) (t/years (or year 10)))))
      (recur (t/plus d (t/days 1))
             (if (pred? d)
               (conj prime-days (f/unparse (f/formatters :date) d))
               prime-days))
      prime-days)))

(def get-all-primes
  (partial get-all-days prime-date?))


(def get-all-palidromes
  (partial get-all-days palindrome-date?))


(def get-prime-and-palindromes
  (partial get-all-days (fn [d]
                          (and (prime-date? d)
                               (palindrome-date? d)))))

(def all-primes (get-all-primes 20))

;; Primes and Palindrome days in the next 10 years
;; ("2021-12-09" "2021-12-03" "2019-09-13" "2018-08-01" "2016-06-11" "2016-06-01")