Add q31

README.md

@@ -4,6 +4,15 @@ A place to keep track of problems/solutions in Clojure.
 
 The problems are from the [4clojure](https://4clojure.oxal.org).
 
+
+## Notes
+
+Handy `clojure.core` functions to keep in mind:
+
+* [`first`](https://clojuredocs.org/clojure.core/first), [`second`](https://clojuredocs.org/clojure.core/second), [`rest`](https://clojuredocs.org/clojure.core/rest), [`nth`](https://clojuredocs.org/clojure.core/nth)
+* [`partition-by`](https://clojuredocs.org/clojure.core/partition-by) and [`group-by`](https://clojuredocs.org/clojure.core/group-by)
+
+
 ## Workflow
 
 1. Get [`just`](https://github.com/casey/just) (`brew install just`)

src/ex/q031.clj

@@ -0,0 +1,8 @@
+;; https://4clojure.oxal.org/#/problem/031
+
+(ns ex.q031)
+
+(defn ans
+  "Problem 31, Pack a Sequence. (pack consecutive duplicates into sub-lists)"
+  [coll]
+  (partition-by identity coll))

test/ex/q031_test.clj

@@ -0,0 +1,11 @@
+;; https://4clojure.oxal.org/#/problem/031
+
+(ns ex.q031-test
+  (:require [clojure.test :as t]
+            [ex.q031 :as sut]))
+
+(t/deftest test-q31
+  (t/testing "Problem 31, Pack a Sequence"
+    (t/is (= '((1 1) (2) (1 1 1) (3 3)) (sut/ans [1 1 2 1 1 1 3 3])))
+    (t/is (= '((:a :a) (:b :b) (:c)) (sut/ans [:a :a :b :b :c])))
+    (t/is (= '(([1 2] [1 2]) ([3 4])) (sut/ans [[1 2] [1 2] [3 4]])))))