anagram: Add new exercise

config.json

@@ -10,6 +10,14 @@
       "topics": [
         "Integers"
       ]
+    },
+    {
+      "slug": "anagram",
+      "difficulty": 4,
+      "topics": [
+        "Strings",
+        "Filtering"
+      ]
     }
   ],
   "deprecated": [

exercises/anagram/example/Anagram.ceylon

@@ -0,0 +1,8 @@
+{String*} anagrams(String subject, {String*} candidates) {
+  value lower = subject.lowercased;
+  value chars = sort(lower);
+  return candidates.filter((c) {
+    value lowerCandidate = c.lowercased;
+    return lower != lowerCandidate && chars == sort(lowerCandidate);
+  });
+}

exercises/anagram/source/anagram/Anagram.ceylon

@@ -0,0 +1,3 @@
+{String*} anagrams(String subject, {String*} candidates) {
+  return nothing;
+}

exercises/anagram/source/anagram/AnagramTest.ceylon

@@ -0,0 +1,47 @@
+import ceylon.test { ... }
+
+shared {[String, {String*}, {String*}]*} cases =>
+  {
+    // no matches
+    ["diaper", {"hello", "world", "zombies", "pants"}, {}],
+    // detects simple anagram
+    ["ant", {"tan", "stand", "at"}, {"tan"}],
+    // does not detect false positives
+    ["galea", {"eagle"}, {}],
+    // detects multiple anagrams
+    ["master", {"stream", "pigeon", "maters"}, {"stream", "maters"}],
+    // does not detect anagram subsets
+    ["good", {"dog", "goody"}, {}],
+    // detects anagram
+    ["listen", {"enlists", "google", "inlets", "banana"}, {"inlets"}],
+    // detects multiple anagrams
+    [
+      "allergy",
+      {"gallery", "ballerina", "regally", "clergy", "largely", "leading"},
+      {"gallery", "regally", "largely"}
+    ],
+    // does not detect identical words
+    ["corn", {"corn", "dark", "Corn", "rank", "CORN", "cron", "park"}, {"cron"}],
+    // does not detect non-anagrams with identical checksum
+    ["mass", {"last"}, {}],
+    // detects anagrams case-insensitively
+    ["Orchestra", {"cashregister", "Carthorse", "radishes"}, {"Carthorse"}],
+    // detects anagrams using case-insensitive subject
+    ["Orchestra", {"cashregister", "carthorse", "radishes"}, {"carthorse"}],
+    // detects anagrams using case-insensitive possible matches
+    ["orchestra", {"cashregister", "Carthorse", "radishes"}, {"Carthorse"}],
+    // does not detect a word as its own anagram
+    ["banana", {"Banana"}, {}],
+    // does not detect a anagram if the original word is repeated
+    ["go", {"go Go GO"}, {}],
+    // anagrams must use all letters exactly once
+    ["tapper", {"patter"}, {}],
+    // capital word is not own anagram
+    ["BANANA", {"Banana"}, {}]
+  };
+
+test
+parameters(`value cases`)
+shared void testAnagram(String subject, {String*} candidates, {String*} expected) {
+  assertEquals(sort(anagrams(subject, candidates)), sort(expected));
+}

exercises/anagram/source/anagram/module.ceylon

@@ -0,0 +1,3 @@
+module anagram "1.0" {
+  import "ceylon.test" "1.3.1";
+}