Add secret-handshake exercise (#397)

config.json

@@ -512,6 +512,14 @@
           "strings"
         ]
       },
+      {
+        "slug": "secret-handshake",
+        "name": "Secret Handshake",
+        "uuid": "e55f5562-9126-4cc7-9f9e-a3cbdfd292b4",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
+      },
       {
         "slug": "series",
         "name": "Series",

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.el"
+    ],
+    "test": [
+      "secret-handshake-test.el"
+    ],
+    "example": [
+      ".meta/example.el"
+    ]
+  },
+  "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.el

@@ -0,0 +1,26 @@
+;;; secret-handshake.el --- Secret Handshake (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+(require 'cl-lib)
+
+(defun commands (number)
+  (let ((all-commands '("wink" "double blink" "close your eyes" "jump"))
+        (result nil))
+    (cl-labels
+      ((extract (action shift pending)
+          (cl-loop until (null pending)
+            if (/= (logand number action) 0)
+              do (setq result (cons (car pending) result))
+            do (setq pending (cdr pending))
+            do (setq action (lsh action shift))
+            finally return result)))
+      (if (= (logand number 16) 0)
+        (funcall #'extract 8 -1 (reverse all-commands))
+        (funcall #'extract 1 1 all-commands)))))
+
+(provide 'secret-handshake)
+;;; secret-handshake.el ends here
+

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-test.el

@@ -0,0 +1,57 @@
+;;; secret-handshake-test.el --- Tests for Secret Handshake (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+
+(load-file "secret-handshake.el")
+(declare-function commands "secret-handshake.el" (number))
+
+
+(ert-deftest wink-for-1 ()
+  (should (equal '("wink") (commands 1))))
+
+
+(ert-deftest double-blink-for-10 ()
+  (should (equal '("double blink") (commands 2))))
+
+
+(ert-deftest close-your-eyes-for-100 ()
+  (should (equal '("close your eyes") (commands 4))))
+
+
+(ert-deftest jump-for-1000 ()
+  (should (equal '("jump") (commands 8))))
+
+
+(ert-deftest combine-two-actions ()
+  (should (equal '("wink" "double blink") (commands 3))))
+
+
+(ert-deftest reverse-two-actions ()
+  (should (equal '("double blink" "wink") (commands 19))))
+
+
+(ert-deftest reversing-one-action-gives-the-same-action ()
+  (should (equal '("jump") (commands 24))))
+
+
+(ert-deftest reversing-no-actions-still-gives-no-actions ()
+  (should (equal '() (commands 16))))
+
+
+(ert-deftest all-possible-actions ()
+  (should (equal '("wink" "double blink" "close your eyes" "jump") (commands 15))))
+
+
+(ert-deftest reverse-all-possible-actions ()
+  (should (equal '("jump" "close your eyes" "double blink" "wink") (commands 31))))
+
+
+(ert-deftest do-nothing-for-zero ()
+  (should (equal '() (commands 0))))
+
+
+(provide 'secret-handshake-test)
+;;; secret-handshake-test.el ends here

exercises/practice/secret-handshake/secret-handshake.el

@@ -0,0 +1,14 @@
+;;; secret-handshake.el --- Secret Handshake (exercism)  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+
+;;; Code:
+
+
+(defun commands (number)
+  (error "Delete this S-Expression and write your own implementation"))
+
+
+(provide 'secret-handshake)
+;;; secret-handshake.el ends here
+