Add accumulate exercise (#110)

config.json

@@ -315,6 +315,16 @@
         "difficulty": 5,
         "topics": null
       },
+      {
+        "slug": "accumulate",
+        "name": "Accumulate",
+        "uuid": "204845d0-73b3-4f68-b8d7-05af5bbff118",
+        "practices": [],
+        "prerequisites": [
+          "numbers"
+        ],
+        "difficulty": 2
+      },
       {
         "slug": "pov",
         "name": "Pov",

exercises/practice/accumulate/.docs/instructions.md

@@ -0,0 +1,22 @@
+# Instructions
+
+Implement the `accumulate` operation, which, given a collection and an operation to perform on each element of the collection, returns a new collection containing the result of applying that operation to each element of the input collection.
+
+Given the collection of numbers:
+
+- 1, 2, 3, 4, 5
+
+And the operation:
+
+- square a number (`x => x * x`)
+
+Your code should be able to produce the collection of squares:
+
+- 1, 4, 9, 16, 25
+
+Check out the test suite to see the expected function signature.
+
+## Restrictions
+
+Keep your hands off that collect/map/fmap/whatchamacallit functionality provided by your standard library!
+Solve this one yourself using other basic tools instead.

exercises/practice/accumulate/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "ErikSchierboom"
+  ],
+  "files": {
+    "solution": [
+      "src/accumulate.cljs"
+    ],
+    "test": [
+      "test/accumulate_test.cljs"
+    ],
+    "example": [
+      ".meta/src/example.cljs"
+    ]
+  },
+  "blurb": "Implement the `accumulate` operation, which, given a collection and an operation to perform on each element of the collection, returns a new collection containing the result of applying that operation to each element of the input collection.",
+  "source": "Conversation with James Edward Gray II",
+  "source_url": "https://twitter.com/jeg2"
+}

exercises/practice/accumulate/.meta/src/example.cljs

@@ -0,0 +1,9 @@
+(ns accumulate)
+
+(defn accumulate [f xs]
+  (loop [xs xs
+         accum []]
+    (if
+     (empty? xs) accum
+     (recur (rest xs) (conj accum (f (first xs)))))))
+

exercises/practice/accumulate/deps.edn

@@ -0,0 +1,10 @@
+{:deps
+ {org.clojure/clojure {:mvn/version "1.10.1"}
+  org.clojure/clojurescript {:mvn/version "1.10.773"}}
+
+ :aliases
+ {:test
+  {:extra-paths ["test"]
+   :extra-deps
+   {olical/cljs-test-runner {:mvn/version "3.8.0"}}
+   :main-opts ["-m" "cljs-test-runner.main"]}}}

exercises/practice/accumulate/src/accumulate.cljs

@@ -0,0 +1,5 @@
+(ns accumulate)
+
+(defn accumulate [] ;; <- arglist goes here
+      ;; your code goes here
+)

exercises/practice/accumulate/test/accumulate_test.cljs

@@ -0,0 +1,30 @@
+(ns accumulate-test
+  (:require [clojure.test :refer [deftest is]]
+            accumulate))
+
+(defn- square [n] (* n n))
+
+(defn- to-s [xs] (apply str xs))
+
+(deftest empty-accumulation
+  (is (= [] (accumulate/accumulate square []))))
+
+(deftest accumulate-squares
+  (is (= [1 4 9] (accumulate/accumulate square [1 2 3]))))
+
+(deftest accumulate-upcases
+  (is (= ["HELLO", "WORLD"]
+         (->> ["hello" "world"]
+              (accumulate/accumulate clojure.string/upper-case)
+              (map to-s)))))
+
+(deftest accumulate-reversed-strings
+  (is (= ["eht" "kciuq" "nworb" "xof" "cte"]
+         (->> ["the" "quick" "brown" "fox" "etc"]
+              (accumulate/accumulate reverse)
+              (map to-s)))))
+
+(deftest accumulate-recursively
+  (is (= [["a1" "a2" "a3"] ["b1" "b2" "b3"] ["c1" "c2" "c3"]]
+         (-> #(accumulate/accumulate (fn [n] (str % n)) [1 2 3])
+             (accumulate/accumulate "abc")))))