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  1. (ns clojurach.core
  2.   (:require [clojure.test :as test :refer [deftest testing is are]]))
  3.  
  4. (defn grep-n [n pred coll]
  5.   (->> coll
  6.        (map-indexed (fn [i x] (clojure.lang.MapEntry. i x)))
  7.        (partition (-> n (* 2) inc) 1)
  8.        (filter #(-> % (nth n) val pred))
  9.        (apply concat)
  10.        distinct
  11.        (map val)))
  12.  
  13. (deftest grep-n-test
  14. 	(is (= '(0) (grep-n 1 #{0} (range 1))))
  15. 	(is (= '(0 1 2) (grep-n 2 #{2} (range 3)))))
  16.  
  17. ;; hack :)
  18.  
  19. (defn grep-n-hack [n pred coll]
  20.   (->> (concat (repeat n ::nil) coll (repeat n ::nil))
  21.        (map-indexed (fn [i x] (clojure.lang.MapEntry. i x)))
  22.        (partition (-> n (* 2) inc) 1)
  23.        (filter #(some-> % (nth n) val pred))
  24.        (apply concat)
  25.        distinct
  26.        (map val)
  27.        (remove #{::nil})))
  28.  
  29. (deftest grep-n-hack-test
  30. 	(is (= '(0) (grep-n-hack 1 #{0} (range 1))))
  31. 	(is (= '(0 1 2) (grep-n-hack 2 #{2} (range 3)))))
  32.  
  33. (test/successful? (test/run-tests))
Success #stdin #stdout 1.58s 89124KB
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Standard input is empty
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Testing clojurach.core

FAIL in (grep-n-test) (prog.clj:14)
expected: (= (quote (0)) (grep-n 1 #{0} (range 1)))
  actual: (not (= (0) ()))

FAIL in (grep-n-test) (prog.clj:15)
expected: (= (quote (0 1 2)) (grep-n 2 #{2} (range 3)))
  actual: (not (= (0 1 2) ()))

Ran 2 tests containing 4 assertions.
2 failures, 0 errors.
https://ideone.com/djTYwk
language:
Clojure (clojure 1.10.0)
created:
6 years ago
visibility:
public

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