Add secret-handshake exercise (#280)

config.json

@@ -132,6 +132,15 @@
         "difficulty": 3,
         "topics": []
       },
+      {
+        "slug": "secret-handshake",
+        "name": "Secret Handshake",
+        "uuid": "55048224-25dc-4c91-b4f4-1ea1bacdd87f",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3,
+        "topics": []
+      },
       {
         "slug": "matching-brackets",
         "name": "Matching Brackets",

exercises/practice/secret-handshake/.docs/instructions.md

@@ -0,0 +1,48 @@
+# Instructions
+
+Your task is to convert a number between 1 and 31 to a sequence of actions in the secret handshake.
+
+The sequence of actions is chosen by looking at the rightmost five digits of the number once it's been converted to binary.
+Start at the right-most digit and move left.
+
+The actions for each number place are:
+
+```plaintext
+00001 = wink
+00010 = double blink
+00100 = close your eyes
+01000 = jump
+10000 = Reverse the order of the operations in the secret handshake.
+```
+
+Let's use the number `9` as an example:
+
+- 9 in binary is `1001`.
+- The digit that is farthest to the right is 1, so the first action is `wink`.
+- Going left, the next digit is 0, so there is no double-blink.
+- Going left again, the next digit is 0, so you leave your eyes open.
+- Going left again, the next digit is 1, so you jump.
+
+That was the last digit, so the final code is:
+
+```plaintext
+wink, jump
+```
+
+Given the number 26, which is `11010` in binary, we get the following actions:
+
+- double blink
+- jump
+- reverse actions
+
+The secret handshake for 26 is therefore:
+
+```plaintext
+jump, double blink
+```
+
+~~~~exercism/note
+If you aren't sure what binary is or how it works, check out [this binary tutorial][intro-to-binary].
+
+[intro-to-binary]: https://medium.com/basecs/bits-bytes-building-with-binary-13cb4289aafa
+~~~~

exercises/practice/secret-handshake/.docs/introduction.md

@@ -0,0 +1,7 @@
+# Introduction
+
+You are starting a secret coding club with some friends and friends-of-friends.
+Not everyone knows each other, so you and your friends have decided to create a secret handshake that you can use to recognize that someone is a member.
+You don't want anyone who isn't in the know to be able to crack the code.
+
+You've designed the code so that one person says a number between 1 and 31, and the other person turns it into a series of actions.

exercises/practice/secret-handshake/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "secret-handshake.sml"
+    ],
+    "test": [
+      "test.sml"
+    ],
+    "example": [
+      ".meta/example.sml"
+    ]
+  },
+  "blurb": "Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.",
+  "source": "Bert, in Mary Poppins",
+  "source_url": "https://www.imdb.com/title/tt0058331/quotes/?item=qt0437047"
+}

exercises/practice/secret-handshake/.meta/example.sml

@@ -0,0 +1,33 @@
+fun commands (number: int): string list =
+  let
+    val wink = 0x1
+    val doubleBlink = 0x2
+    val closeYourEyes = 0x4
+    val jump = 0x8
+    val reverse = 0x10
+
+    fun isChosen (action: int): bool =
+      Word.andb (Word.fromInt number, Word.fromInt action) <> Word.fromInt 0
+
+    fun conditionallyPrefix (action: int, command: string) (l: string list): string list =
+      if isChosen action then command :: l
+      else l
+
+    val conditionallyWink: string list -> string list =
+      conditionallyPrefix (wink, "wink")
+
+    val conditionallyDoubleBlink: string list -> string list =
+      conditionallyPrefix (doubleBlink, "double blink")
+
+    val conditionallyCloseYourEyes: string list -> string list =
+      conditionallyPrefix (closeYourEyes, "close your eyes")
+
+    val conditionallyJump: string list -> string list =
+      conditionallyPrefix (jump, "jump")
+
+    fun conditionallyReverse l =
+      if isChosen reverse then rev l
+      else l
+  in
+    (conditionallyReverse o conditionallyWink o conditionallyDoubleBlink o conditionallyCloseYourEyes o conditionallyJump) []
+  end

exercises/practice/secret-handshake/.meta/tests.toml

@@ -0,0 +1,43 @@
+# 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.
+
+[b8496fbd-6778-468c-8054-648d03c4bb23]
+description = "wink for 1"
+
+[83ec6c58-81a9-4fd1-bfaf-0160514fc0e3]
+description = "double blink for 10"
+
+[0e20e466-3519-4134-8082-5639d85fef71]
+description = "close your eyes for 100"
+
+[b339ddbb-88b7-4b7d-9b19-4134030d9ac0]
+description = "jump for 1000"
+
+[40499fb4-e60c-43d7-8b98-0de3ca44e0eb]
+description = "combine two actions"
+
+[9730cdd5-ef27-494b-afd3-5c91ad6c3d9d]
+description = "reverse two actions"
+
+[0b828205-51ca-45cd-90d5-f2506013f25f]
+description = "reversing one action gives the same action"
+
+[9949e2ac-6c9c-4330-b685-2089ab28b05f]
+description = "reversing no actions still gives no actions"
+
+[23fdca98-676b-4848-970d-cfed7be39f81]
+description = "all possible actions"
+
+[ae8fe006-d910-4d6f-be00-54b7c3799e79]
+description = "reverse all possible actions"
+
+[3d36da37-b31f-4cdb-a396-d93a2ee1c4a5]
+description = "do nothing for zero"

exercises/practice/secret-handshake/secret-handshake.sml

@@ -0,0 +1,2 @@
+fun commands (number: int): string list =
+  raise Fail "'commands' is not implemented"

exercises/practice/secret-handshake/test.sml

@@ -0,0 +1,89 @@
+(* version 1.0.0 *)
+
+use "testlib.sml";
+use "secret-handshake.sml";
+
+infixr |>
+fun x |> f = f x
+
+val testsuite =
+  describe "secret-handshake" [
+    test "wink for 1"
+      (fn _ => let
+        val expected = ["wink"]
+      in
+        commands 1 |> Expect.equalTo expected
+      end),
+
+    test "double blink for 10"
+      (fn _ => let
+        val expected = ["double blink"]
+      in
+        commands 2 |> Expect.equalTo expected
+      end),
+
+    test "close your eyes for 100"
+      (fn _ => let
+        val expected = ["close your eyes"]
+      in
+        commands 4 |> Expect.equalTo expected
+      end),
+
+    test "jump for 1000"
+      (fn _ => let
+        val expected = ["jump"]
+      in
+        commands 8 |> Expect.equalTo expected
+      end),
+
+    test "combine two actions"
+      (fn _ => let
+        val expected = ["wink", "double blink"]
+      in
+        commands 3 |> Expect.equalTo expected
+      end),
+
+    test "reverse two actions"
+      (fn _ => let
+        val expected = ["double blink", "wink"]
+      in
+        commands 19 |> Expect.equalTo expected
+      end),
+
+    test "reversing one action gives the same action"
+      (fn _ => let
+        val expected = ["jump"]
+      in
+        commands 24 |> Expect.equalTo expected
+      end),
+
+    test "reversing no actions still gives no actions"
+      (fn _ => let
+        val expected = []
+      in
+        commands 16 |> Expect.equalTo expected
+      end),
+
+    test "all possible actions"
+      (fn _ => let
+        val expected = ["wink", "double blink", "close your eyes", "jump"]
+      in
+        commands 15 |> Expect.equalTo expected
+      end),
+
+    test "reverse all possible actions"
+      (fn _ => let
+        val expected = ["jump", "close your eyes", "double blink", "wink"]
+      in
+        commands 31 |> Expect.equalTo expected
+      end),
+
+    test "do nothing for zero"
+      (fn _ => let
+        val expected = []
+      in
+        commands 0 |> Expect.equalTo expected
+      end)
+  ]
+
+val _ = Test.run testsuite