Add exercise 'square-root' (#245)

config.json

@@ -105,6 +105,17 @@
           "stacks"
         ]
       },
+      {
+        "slug": "square-root",
+        "name": "Square Root",
+        "uuid": "8f79d2ac-2407-4bba-91a8-6a47737e7f36",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4,
+        "topics": [
+          "math"
+        ]
+      },
       {
         "slug": "allergies",
         "name": "Allergies",
@@ -332,8 +343,8 @@
         "prerequisites": [],
         "difficulty": 1,
         "topics": [
-            "lists",
-            "strings"
+          "lists",
+          "strings"
         ]
       },
       {
@@ -344,9 +355,9 @@
         "prerequisites": [],
         "difficulty": 1,
         "topics": [
-            "lists",
-            "strings",
-            "text_formatting"
+          "lists",
+          "strings",
+          "text_formatting"
         ]
       },
       {
@@ -398,7 +409,7 @@
     ]
   },
   "concepts": [],
-    "key_features": [
+  "key_features": [
     {
       "title": "Algebraic data types",
       "content": "Easy to define and easy to use, with robust pattern matching and pattern-exhaustiveness.",

exercises/practice/square-root/.docs/instructions.md

@@ -0,0 +1,13 @@
+# Instructions
+
+Given a natural radicand, return its square root.
+
+Note that the term "radicand" refers to the number for which the root is to be determined.
+That is, it is the number under the root symbol.
+
+Check out the Wikipedia pages on [square root][square-root] and [methods of computing square roots][computing-square-roots].
+
+Recall also that natural numbers are positive real whole numbers (i.e. 1, 2, 3 and up).
+
+[square-root]: https://en.wikipedia.org/wiki/Square_root
+[computing-square-roots]: https://en.wikipedia.org/wiki/Methods_of_computing_square_roots

exercises/practice/square-root/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "square-root.sml"
+    ],
+    "test": [
+      "test.sml"
+    ],
+    "example": [
+      ".meta/example.sml"
+    ]
+  },
+  "blurb": "Given a natural radicand, return its square root.",
+  "source": "wolf99",
+  "source_url": "https://github.com/exercism/problem-specifications/pull/1582"
+}

exercises/practice/square-root/.meta/example.sml

@@ -0,0 +1,19 @@
+(* We use Heron's method, with rounding to the nearest natural number.
+ * https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Heron's_method
+ * estimate = (guess + randicand / guess) / 2
+ *          = (guess * guess + randicand) / (2 * guess)
+ * To achieve rounding when using integer division,
+ * we must increase the numerator by half the denominator.
+ *)
+fun squareRoot (radicand: int): int =
+  let
+    fun recurse guess =
+      let
+        val estimate = (guess * (guess + 1) + radicand) div (2 * guess)
+      in
+        if estimate = guess then estimate
+        else recurse estimate
+      end
+  in
+    recurse 1
+  end

exercises/practice/square-root/.meta/tests.toml

@@ -0,0 +1,28 @@
+# 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.
+
+[9b748478-7b0a-490c-b87a-609dacf631fd]
+description = "root of 1"
+
+[7d3aa9ba-9ac6-4e93-a18b-2e8b477139bb]
+description = "root of 4"
+
+[6624aabf-3659-4ae0-a1c8-25ae7f33c6ef]
+description = "root of 25"
+
+[93beac69-265e-4429-abb1-94506b431f81]
+description = "root of 81"
+
+[fbddfeda-8c4f-4bc4-87ca-6991af35360e]
+description = "root of 196"
+
+[c03d0532-8368-4734-a8e0-f96a9eb7fc1d]
+description = "root of 65025"

exercises/practice/square-root/square-root.sml

@@ -0,0 +1,2 @@
+fun squareRoot (radicand: int): int =
+  raise Fail "'squareRoot' is not implemented"

exercises/practice/square-root/test.sml

@@ -0,0 +1,30 @@
+(* version 1.0.0 *)
+
+use "testlib.sml";
+use "square-root.sml";
+
+infixr |>
+fun x |> f = f x
+
+val testsuite =
+  describe "square-root" [
+    test "root of 1"
+      (fn _ => squareRoot 1 |> Expect.equalTo 1),
+
+    test "root of 4"
+      (fn _ => squareRoot 4 |> Expect.equalTo 2),
+
+    test "root of 25"
+      (fn _ => squareRoot 25 |> Expect.equalTo 5),
+
+    test "root of 81"
+      (fn _ => squareRoot 81 |> Expect.equalTo 9),
+
+    test "root of 196"
+      (fn _ => squareRoot 196 |> Expect.equalTo 14),
+
+    test "root of 65025"
+      (fn _ => squareRoot 65025 |> Expect.equalTo 255)
+  ]
+
+val _ = Test.run testsuite

exercises/practice/square-root/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)