Add isogram exercise (#253)

config.json

@@ -313,6 +313,17 @@
         "difficulty": 1,
         "topics": []
       },
+      {
+        "slug": "isogram",
+        "name": "Isogram",
+        "uuid": "ae8fa578-1308-44b2-8e71-d7566553379c",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3,
+        "topics": [
+          "strings"
+        ]
+      },
       {
         "slug": "pig-latin",
         "name": "Pig Latin",

exercises/practice/isogram/.docs/instructions.md

@@ -0,0 +1,14 @@
+# Instructions
+
+Determine if a word or phrase is an isogram.
+
+An isogram (also known as a "non-pattern word") is a word or phrase without a repeating letter, however spaces and hyphens are allowed to appear multiple times.
+
+Examples of isograms:
+
+- lumberjacks
+- background
+- downstream
+- six-year-old
+
+The word _isograms_, however, is not an isogram, because the s repeats.

exercises/practice/isogram/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "isogram.sml"
+    ],
+    "test": [
+      "test.sml"
+    ],
+    "example": [
+      ".meta/example.sml"
+    ]
+  },
+  "blurb": "Determine if a word or phrase is an isogram.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Isogram"
+}

exercises/practice/isogram/.meta/example.sml

@@ -0,0 +1,28 @@
+val isIsogram: string -> bool =
+  let
+    val a = Char.ord #"a"
+
+    (* We represent each letter by setting a different bit,
+     * for example the letter c is encoded as ...00100 binary.
+     *)
+    fun letterValue (c: char): word =
+      Word.<<(0wx1, Word.fromInt(Char.ord (Char.toLower c) - a))
+
+    (* seen represents the set of letters that have been seen
+     * so far. For example, if we have seen the letters d and c,
+     * this is encoded as ...01100 binary.
+     * If we find a letter in l that matches a letter already
+     * seen, we return false.
+     *)
+    fun recurse (seen: word) (l: char list): bool =
+      case l of
+          nil => true
+        | c :: rest =>
+            let
+              val seen' = Word.orb (seen, letterValue c)
+            in
+              seen' <> seen andalso recurse seen' rest
+            end
+  in
+    recurse 0wx0 o List.filter Char.isAlpha o String.explode
+  end

exercises/practice/isogram/.meta/tests.toml

@@ -0,0 +1,52 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[a0e97d2d-669e-47c7-8134-518a1e2c4555]
+description = "empty string"
+
+[9a001b50-f194-4143-bc29-2af5ec1ef652]
+description = "isogram with only lower case characters"
+
+[8ddb0ca3-276e-4f8b-89da-d95d5bae78a4]
+description = "word with one duplicated character"
+
+[6450b333-cbc2-4b24-a723-0b459b34fe18]
+description = "word with one duplicated character from the end of the alphabet"
+
+[a15ff557-dd04-4764-99e7-02cc1a385863]
+description = "longest reported english isogram"
+
+[f1a7f6c7-a42f-4915-91d7-35b2ea11c92e]
+description = "word with duplicated character in mixed case"
+
+[14a4f3c1-3b47-4695-b645-53d328298942]
+description = "word with duplicated character in mixed case, lowercase first"
+
+[423b850c-7090-4a8a-b057-97f1cadd7c42]
+description = "hypothetical isogrammic word with hyphen"
+
+[93dbeaa0-3c5a-45c2-8b25-428b8eacd4f2]
+description = "hypothetical word with duplicated character following hyphen"
+
+[36b30e5c-173f-49c6-a515-93a3e825553f]
+description = "isogram with duplicated hyphen"
+
+[cdabafa0-c9f4-4c1f-b142-689c6ee17d93]
+description = "made-up name that is an isogram"
+
+[5fc61048-d74e-48fd-bc34-abfc21552d4d]
+description = "duplicated character in the middle"
+
+[310ac53d-8932-47bc-bbb4-b2b94f25a83e]
+description = "same first and last characters"
+
+[0d0b8644-0a1e-4a31-a432-2b3ee270d847]
+description = "word with duplicated character and with two hyphens"

exercises/practice/isogram/isogram.sml

@@ -0,0 +1,2 @@
+fun isIsogram s =
+  raise Fail "'isIsogram' is not implemented"

exercises/practice/isogram/test.sml

@@ -0,0 +1,54 @@
+(* version 1.0.0 *)
+
+use "testlib.sml";
+use "isogram.sml";
+
+infixr |>
+fun x |> f = f x
+
+val testsuite =
+  describe "isogram" [
+    test "empty string"
+      (fn _ => isIsogram "" |> Expect.truthy),
+
+    test "isogram with only lower case characters"
+      (fn _ => isIsogram "isogram" |> Expect.truthy),
+
+    test "word with one duplicated character"
+      (fn _ => isIsogram "eleven" |> Expect.falsy),
+
+    test "word with one duplicated character from the end of the alphabet"
+      (fn _ => isIsogram "zzyzx" |> Expect.falsy),
+
+    test "longest reported english isogram"
+      (fn _ => isIsogram "subdermatoglyphic" |> Expect.truthy),
+
+    test "word with duplicated character in mixed case"
+      (fn _ => isIsogram "Alphabet" |> Expect.falsy),
+
+    test "word with duplicated character in mixed case, lowercase first"
+      (fn _ => isIsogram "alphAbet" |> Expect.falsy),
+
+    test "hypothetical isogrammic word with hyphen"
+      (fn _ => isIsogram "thumbscrew-japingly" |> Expect.truthy),
+
+    test "hypothetical word with duplicated character following hyphen"
+      (fn _ => isIsogram "thumbscrew-jappingly" |> Expect.falsy),
+
+    test "isogram with duplicated hyphen"
+      (fn _ => isIsogram "six-year-old" |> Expect.truthy),
+
+    test "made-up name that is an isogram"
+      (fn _ => isIsogram "Emily Jung Schwartzkopf" |> Expect.truthy),
+
+    test "duplicated character in the middle"
+      (fn _ => isIsogram "accentor" |> Expect.falsy),
+
+    test "same first and last characters"
+      (fn _ => isIsogram "angola" |> Expect.falsy),
+
+    test "word with duplicated character and with two hyphens"
+      (fn _ => isIsogram "up-to-date" |> Expect.falsy)
+  ]
+
+val _ = Test.run testsuite

exercises/practice/isogram/testlib.sml

@@ -0,0 +1,160 @@
+structure Expect =
+struct
+  datatype expectation = Pass | Fail of string * string
+
+  local
+    fun failEq b a =
+      Fail ("Expected: " ^ b, "Got: " ^ a)
+
+    fun failExn b a =
+      Fail ("Expected: " ^ b, "Raised: " ^ a)
+
+    fun exnName (e: exn): string = General.exnName e
+  in
+    fun truthy a =
+      if a
+      then Pass
+      else failEq "true" "false"
+
+    fun falsy a =
+      if a
+      then failEq "false" "true"
+      else Pass
+
+    fun equalTo b a = 
+      if a = b
+      then Pass
+      else failEq (PolyML.makestring b) (PolyML.makestring a)
+
+    fun nearTo delta b a =
+      if Real.abs (a - b) <= delta * Real.abs a orelse
+         Real.abs (a - b) <= delta * Real.abs b
+      then Pass
+      else failEq (Real.toString b ^ " +/- " ^ Real.toString delta) (Real.toString a)
+
+    fun anyError f =
+      (
+        f ();
+        failExn "an exception" "Nothing"
+      ) handle _ => Pass
+
+    fun error e f =
+      (
+        f ();
+        failExn (exnName e) "Nothing"
+      ) handle e' => if exnMessage e' = exnMessage e
+                     then Pass
+                     else failExn (exnMessage e) (exnMessage e')
+  end
+end
+
+structure TermColor =
+struct
+  datatype color = Red | Green | Yellow | Normal
+
+  fun f Red    = "\027[31m"
+    | f Green  = "\027[32m"
+    | f Yellow = "\027[33m"
+    | f Normal = "\027[0m"
+
+  fun colorize color s = (f color) ^ s ^ (f Normal)
+
+  val redit = colorize Red
+
+  val greenit = colorize Green
+
+  val yellowit = colorize Yellow
+end
+
+structure Test =
+struct
+  datatype testnode = TestGroup of string * testnode list
+                    | Test of string * (unit -> Expect.expectation)
+
+  local
+    datatype evaluation = Success of string
+                        | Failure of string * string * string
+                        | Error of string * string
+
+    fun indent n s = (implode (List.tabulate (n, fn _ => #" "))) ^ s
+
+    fun fmt indentlvl ev =
+      let
+        val check = TermColor.greenit "\226\156\148 " (* ✔ *)
+        val cross = TermColor.redit "\226\156\150 "   (* ✖ *)
+        val indentlvl = indentlvl * 2
+      in
+      case ev of
+        Success descr => indent indentlvl (check ^ descr)
+      | Failure (descr, exp, got) =>
+          String.concatWith "\n" [indent indentlvl (cross ^ descr),
+                                  indent (indentlvl + 2) exp,
+                                  indent (indentlvl + 2) got]
+      | Error (descr, reason) =>
+          String.concatWith "\n" [indent indentlvl (cross ^ descr),
+                                  indent (indentlvl + 2) (TermColor.redit reason)]
+      end
+
+    fun eval (TestGroup _) = raise Fail "Only a 'Test' can be evaluated"
+      | eval (Test (descr, thunk)) =
+          (
+            case thunk () of
+              Expect.Pass   => ((1, 0, 0), Success descr)
+            | Expect.Fail (s, s') => ((0, 1, 0), Failure (descr, s, s'))
+          )
+          handle e => ((0, 0, 1), Error (descr, "Unexpected error: " ^ exnMessage e))
+
+    fun flatten depth testnode =
+      let
+        fun sum (x, y, z) (a, b, c) = (x + a, y + b, z + c)
+
+        fun aux (t, (counter, acc)) =
+          let
+            val (counter', texts) = flatten (depth + 1) t
+          in
+            (sum counter' counter, texts :: acc)
+          end
+      in
+        case testnode of
+          TestGroup (descr, ts) =>
+            let
+              val (counter, texts) = foldr aux ((0, 0, 0), []) ts
+            in
+              (counter, (indent (depth * 2) descr) :: List.concat texts)
+            end
+        | Test _ =>
+            let
+              val (counter, evaluation) = eval testnode
+            in
+              (counter, [fmt depth evaluation])
+            end
+      end
+
+    fun println s = print (s ^ "\n")
+  in
+    fun run suite =
+      let
+        val ((succeeded, failed, errored), texts) = flatten 0 suite
+
+        val summary = String.concatWith ", " [
+          TermColor.greenit ((Int.toString succeeded) ^ " passed"),
+          TermColor.redit ((Int.toString failed) ^ " failed"),
+          TermColor.redit ((Int.toString errored) ^ " errored"),
+          (Int.toString (succeeded + failed + errored)) ^ " total"
+        ]
+
+        val status = if failed = 0 andalso errored = 0
+                     then OS.Process.success
+                     else OS.Process.failure
+
+      in
+        List.app println texts;
+        println "";
+        println ("Tests: " ^ summary);
+        OS.Process.exit status
+      end
+  end
+end
+
+fun describe description tests = Test.TestGroup (description, tests)
+fun test description thunk = Test.Test (description, thunk)