(require '[clojure.string :as str])

(def numbers [2 3 5 7 11 13 17 19])

;; Clojure has no "break": a loop ends simply by not calling recur
(def s
  (loop [[n & more] numbers, acc []]
    (if (or (nil? n) (> n 10))
      (str/join "-" acc)
      (recur more (conj acc n)))))
;; s is "2-3-5-7"
(println "s is" s)

;; inside reduce the early exit is "reduced"
(println "with reduce:"
         (str/join "-" (reduce (fn [acc n]
                                 (if (> n 10) (reduced acc) (conj acc n)))
                               []
                               numbers)))

;; and said declaratively it is just take-while
(println "with take-while:" (str/join "-" (take-while #(<= % 10) numbers)))