Screencast link: https://youtu.be/-Ul-XbIUiqE
See also chapter 3.4.2 of the Clojure Standard Library book.
"Clojure Pills - 004 range"
;; longs, pos and neg
(range 10)
(range 5 10)
(range 0 10 2)
(range 20 10 -2)
;; doubles and ratios
(range 0 5 0.5)
(range 0 1 1/10)
(take 5 (range))
;; auto-promotion
(range (-' Long/MAX_VALUE 3) (+' Long/MAX_VALUE 3))
(map type (range (-' Long/MAX_VALUE 3) (+' Long/MAX_VALUE 3)))
;; checking for palindrome sequences
(def s "was it a car or a cat i saw")
(defn palindrome? [xs]
(let [cnt (count xs) idx (range (quot cnt 2) 0 -1)]
(every? #(= (nth xs (dec %) ) (nth xs (- cnt %))) idx)))
(palindrome? (remove #(= \space %) s))
;; true
(def s-2 "was it e car or a cat i saw")
(palindrome? (remove #(= \space %) s-2))
;; false
;; see also iterate
(source range)
(take 10 (iterate not true))
;; range laziness
(def s (range 1e20))
(def xs (map #(do (print ".") %) (range 100)))
(take 5 xs)
(last (take 33 xs))
;; at the profiler (see below)
(last (range 1000000000))
Visualizing range laziness at the profiler. In general you need to pay attention at not retaining the head of the sequence, which sometimes happens in subtle ways.
