Add matrix exercise (#268)

config.json

@@ -143,6 +143,17 @@
           "stacks"
         ]
       },
+      {
+        "slug": "matrix",
+        "name": "Matrix",
+        "uuid": "892922b8-1616-41f5-9faa-11eb0f776cce",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4,
+        "topics": [
+          "lists"
+        ]
+      },
       {
         "slug": "square-root",
         "name": "Square Root",

exercises/practice/matrix/.docs/instructions.md

@@ -0,0 +1,38 @@
+# Instructions
+
+Given a string representing a matrix of numbers, return the rows and columns of that matrix.
+
+So given a string with embedded newlines like:
+
+```text
+9 8 7
+5 3 2
+6 6 7
+```
+
+representing this matrix:
+
+```text
+    1  2  3
+  |---------
+1 | 9  8  7
+2 | 5  3  2
+3 | 6  6  7
+```
+
+your code should be able to spit out:
+
+- A list of the rows, reading each row left-to-right while moving top-to-bottom across the rows,
+- A list of the columns, reading each column top-to-bottom while moving from left-to-right.
+
+The rows for our example matrix:
+
+- 9, 8, 7
+- 5, 3, 2
+- 6, 6, 7
+
+And its columns:
+
+- 9, 5, 6
+- 8, 3, 6
+- 7, 2, 7

exercises/practice/matrix/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "matrix.sml"
+    ],
+    "test": [
+      "test.sml"
+    ],
+    "example": [
+      ".meta/example.sml"
+    ]
+  },
+  "blurb": "Given a string representing a matrix of numbers, return the rows and columns of that matrix.",
+  "source": "Exercise by the JumpstartLab team for students at The Turing School of Software and Design.",
+  "source_url": "https://turing.edu"
+}

exercises/practice/matrix/.meta/example.sml

@@ -0,0 +1,17 @@
+local
+  val lines: string -> string list =
+    String.tokens (fn (c: char) => c = #"\n")
+
+  val cells: string -> string list =
+    String.tokens (fn (c: char) => c = #" ")
+
+  fun extract (index: int) (l: string list): string =
+    List.nth (l, index - 1)
+in
+  fun row (s: string, index: int): int list =
+    map (valOf o Int.fromString) ((cells o extract index o lines) s)
+
+  fun column (s: string, index: int): int list =
+    map (valOf o Int.fromString o extract index o cells) (lines s)
+end
+

exercises/practice/matrix/.meta/tests.toml

@@ -0,0 +1,34 @@
+# 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.
+
+[ca733dab-9d85-4065-9ef6-a880a951dafd]
+description = "extract row from one number matrix"
+
+[5c93ec93-80e1-4268-9fc2-63bc7d23385c]
+description = "can extract row"
+
+[2f1aad89-ad0f-4bd2-9919-99a8bff0305a]
+description = "extract row where numbers have different widths"
+
+[68f7f6ba-57e2-4e87-82d0-ad09889b5204]
+description = "can extract row from non-square matrix with no corresponding column"
+
+[e8c74391-c93b-4aed-8bfe-f3c9beb89ebb]
+description = "extract column from one number matrix"
+
+[7136bdbd-b3dc-48c4-a10c-8230976d3727]
+description = "can extract column"
+
+[ad64f8d7-bba6-4182-8adf-0c14de3d0eca]
+description = "can extract column from non-square matrix with no corresponding row"
+
+[9eddfa5c-8474-440e-ae0a-f018c2a0dd89]
+description = "extract column where numbers have different widths"

exercises/practice/matrix/matrix.sml

@@ -0,0 +1,6 @@
+fun row (s: string, index: int): int list =
+  raise Fail "'row' is not implemented"
+
+fun column (s: string, index: int): int list =
+  raise Fail "'column' is not implemented"
+

exercises/practice/matrix/test.sml

@@ -0,0 +1,68 @@
+(* version 1.0.0 *)
+
+use "testlib.sml";
+use "matrix.sml";
+
+infixr |>
+fun x |> f = f x
+
+val testsuite =
+  describe "matrix" [
+    test "extract row from one number matrix"
+      (fn _ => let
+        val s = "1"
+      in
+        row (s, 1) |> Expect.equalTo [1]
+      end),
+
+    test "can extract row"
+      (fn _ => let
+        val s = "1 2\n3 4"
+      in
+        row (s, 2) |> Expect.equalTo [3, 4]
+      end),
+
+    test "extract row where numbers have different widths"
+      (fn _ => let
+        val s = "1 2\n10 20"
+      in
+        row (s, 2) |> Expect.equalTo [10, 20]
+      end),
+
+    test "can extract row from non-square matrix with no corresponding column"
+      (fn _ => let
+        val s = "1 2 3\n4 5 6\n7 8 9\n8 7 6"
+      in
+        row (s, 4) |> Expect.equalTo [8, 7, 6]
+      end),
+
+    test "extract column from one number matrix"
+      (fn _ => let
+        val s = "1"
+      in
+        column (s, 1) |> Expect.equalTo [1]
+      end),
+
+    test "can extract column"
+      (fn _ => let
+        val s = "1 2 3\n4 5 6\n7 8 9"
+      in
+        column (s, 3) |> Expect.equalTo [3, 6, 9]
+      end),
+
+    test "can extract column from non-square matrix with no corresponding row"
+      (fn _ => let
+        val s = "1 2 3 4\n5 6 7 8\n9 8 7 6"
+      in
+        column (s, 4) |> Expect.equalTo [4, 8, 6]
+      end),
+
+    test "extract column where numbers have different widths"
+      (fn _ => let
+        val s = "89 1903 3\n18 3 1\n9 4 800"
+      in
+        column (s, 2) |> Expect.equalTo [1903, 3, 4]
+      end)
+  ]
+
+val _ = Test.run testsuite

exercises/practice/matrix/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)