Add atbash-cipher

config.json

@@ -58,6 +58,14 @@
         "prerequisites": [],
         "difficulty": 2
       },
+      {
+        "slug": "atbash-cipher",
+        "name": "Atbash Cipher",
+        "uuid": "e63adab3-3824-499f-b6d7-e052fb04844c",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "binary-search",
         "name": "Binary Search",

exercises/practice/atbash-cipher/.docs/instructions.md

@@ -0,0 +1,27 @@
+# Instructions
+
+Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.
+
+The Atbash cipher is a simple substitution cipher that relies on transposing all the letters in the alphabet such that the resulting alphabet is backwards.
+The first letter is replaced with the last letter, the second with the second-last, and so on.
+
+An Atbash cipher for the Latin alphabet would be as follows:
+
+```text
+Plain:  abcdefghijklmnopqrstuvwxyz
+Cipher: zyxwvutsrqponmlkjihgfedcba
+```
+
+It is a very weak cipher because it only has one possible key, and it is a simple mono-alphabetic substitution cipher.
+However, this may not have been an issue in the cipher's time.
+
+Ciphertext is written out in groups of fixed length, the traditional group size being 5 letters, leaving numbers unchanged, and punctuation is excluded.
+This is to make it harder to guess things based on word boundaries.
+All text will be encoded as lowercase letters.
+
+## Examples
+
+- Encoding `test` gives `gvhg`
+- Encoding `x123 yes` gives `c123b vh`
+- Decoding `gvhg` gives `test`
+- Decoding `gsvjf rxpyi ldmul cqfnk hlevi gsvoz abwlt` gives `thequickbrownfoxjumpsoverthelazydog`

exercises/practice/atbash-cipher/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "atbash-cipher.red"
+    ],
+    "test": [
+      "atbash-cipher-test.red"
+    ],
+    "example": [
+      ".meta/example.red"
+    ]
+  },
+  "blurb": "Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Atbash"
+}

exercises/practice/atbash-cipher/.meta/example.red

@@ -0,0 +1,62 @@
+Red [
+	description: {"Atbash Cipher" exercise solution for exercism platform}
+	author: "BNAndras"
+]
+
+encode: function [
+	phrase
+] [
+	count: 0
+	result: copy ""
+
+	foreach char lowercase phrase [
+		if or~ whitespace? char punctuation? char [continue]
+
+
+		if count = 5 [
+			append result #" "
+			count: 0
+		]
+
+		encoded: char
+		if and~ char >= #"a" char <= #"z" [
+			encoded: to-char (#"z" - char + #"a")
+		]
+
+		append result encoded
+
+		count: count + 1
+	]
+
+	result
+]
+
+decode: function [
+	phrase
+] [
+	count: 0
+	result: copy ""
+
+	foreach char phrase [
+		if and~ char >= #"a" char <= #"z" [
+			append result to-char (#"z" - char + #"a")
+		]
+		if and~ char >= #"0" char <= #"9" [
+			append result char
+		]
+	]
+
+	result
+]
+
+whitespace?: function [
+	char
+] [
+	parse to-string char [any [" " | tab | newline]]
+]
+
+punctuation?: function [
+	char
+] [
+	parse to-string char [any [#"." | "," | "!" | "?" | "'" ]]
+]

exercises/practice/atbash-cipher/.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.
+
+[2f47ebe1-eab9-4d6b-b3c6-627562a31c77]
+description = "encode -> encode yes"
+
+[b4ffe781-ea81-4b74-b268-cc58ba21c739]
+description = "encode -> encode no"
+
+[10e48927-24ab-4c4d-9d3f-3067724ace00]
+description = "encode -> encode OMG"
+
+[d59b8bc3-509a-4a9a-834c-6f501b98750b]
+description = "encode -> encode spaces"
+
+[31d44b11-81b7-4a94-8b43-4af6a2449429]
+description = "encode -> encode mindblowingly"
+
+[d503361a-1433-48c0-aae0-d41b5baa33ff]
+description = "encode -> encode numbers"
+
+[79c8a2d5-0772-42d4-b41b-531d0b5da926]
+description = "encode -> encode deep thought"
+
+[9ca13d23-d32a-4967-a1fd-6100b8742bab]
+description = "encode -> encode all the letters"
+
+[bb50e087-7fdf-48e7-9223-284fe7e69851]
+description = "decode -> decode exercism"
+
+[ac021097-cd5d-4717-8907-b0814b9e292c]
+description = "decode -> decode a sentence"
+
+[18729de3-de74-49b8-b68c-025eaf77f851]
+description = "decode -> decode numbers"
+
+[0f30325f-f53b-415d-ad3e-a7a4f63de034]
+description = "decode -> decode all the letters"
+
+[39640287-30c6-4c8c-9bac-9d613d1a5674]
+description = "decode -> decode with too many spaces"
+
+[b34edf13-34c0-49b5-aa21-0768928000d5]
+description = "decode -> decode with no spaces"

exercises/practice/atbash-cipher/atbash-cipher-test.red

@@ -0,0 +1,136 @@
+Red [
+	description: {Tests for "Atbash Cipher" Exercism exercise}
+	author: "loziniak"
+]
+
+#include %testlib.red
+
+test-init/limit %atbash-cipher.red 1
+; test-init/limit %.meta/example.red 1						; test example solution
+
+canonical-cases: [#[
+    description: "encode yes"
+    input: #[
+        phrase: "yes"
+    ]
+    expected: "bvh"
+    function: "encode"
+    uuid: "2f47ebe1-eab9-4d6b-b3c6-627562a31c77"
+] #[
+    description: "encode no"
+    input: #[
+        phrase: "no"
+    ]
+    expected: "ml"
+    function: "encode"
+    uuid: "b4ffe781-ea81-4b74-b268-cc58ba21c739"
+] #[
+    description: "encode OMG"
+    input: #[
+        phrase: "OMG"
+    ]
+    expected: "lnt"
+    function: "encode"
+    uuid: "10e48927-24ab-4c4d-9d3f-3067724ace00"
+] #[
+    description: "encode spaces"
+    input: #[
+        phrase: "O M G"
+    ]
+    expected: "lnt"
+    function: "encode"
+    uuid: "d59b8bc3-509a-4a9a-834c-6f501b98750b"
+] #[
+    description: "encode mindblowingly"
+    input: #[
+        phrase: "mindblowingly"
+    ]
+    expected: "nrmwy oldrm tob"
+    function: "encode"
+    uuid: "31d44b11-81b7-4a94-8b43-4af6a2449429"
+] #[
+    description: "encode numbers"
+    input: #[
+        phrase: "Testing,1 2 3, testing."
+    ]
+    expected: "gvhgr mt123 gvhgr mt"
+    function: "encode"
+    uuid: "d503361a-1433-48c0-aae0-d41b5baa33ff"
+] #[
+    description: "encode deep thought"
+    input: #[
+        phrase: "Truth is fiction."
+    ]
+    expected: "gifgs rhurx grlm"
+    function: "encode"
+    uuid: "79c8a2d5-0772-42d4-b41b-531d0b5da926"
+] #[
+    description: "encode all the letters"
+    input: #[
+        phrase: "The quick brown fox jumps over the lazy dog."
+    ]
+    expected: "gsvjf rxpyi ldmul cqfnk hlevi gsvoz abwlt"
+    function: "encode"
+    uuid: "9ca13d23-d32a-4967-a1fd-6100b8742bab"
+] #[
+    description: "decode exercism"
+    input: #[
+        phrase: "vcvix rhn"
+    ]
+    expected: "exercism"
+    function: "decode"
+    uuid: "bb50e087-7fdf-48e7-9223-284fe7e69851"
+] #[
+    description: "decode a sentence"
+    input: #[
+        phrase: "zmlyh gzxov rhlug vmzhg vkkrm thglm v"
+    ]
+    expected: "anobstacleisoftenasteppingstone"
+    function: "decode"
+    uuid: "ac021097-cd5d-4717-8907-b0814b9e292c"
+] #[
+    description: "decode numbers"
+    input: #[
+        phrase: "gvhgr mt123 gvhgr mt"
+    ]
+    expected: "testing123testing"
+    function: "decode"
+    uuid: "18729de3-de74-49b8-b68c-025eaf77f851"
+] #[
+    description: "decode all the letters"
+    input: #[
+        phrase: "gsvjf rxpyi ldmul cqfnk hlevi gsvoz abwlt"
+    ]
+    expected: "thequickbrownfoxjumpsoverthelazydog"
+    function: "decode"
+    uuid: "0f30325f-f53b-415d-ad3e-a7a4f63de034"
+] #[
+    description: "decode with too many spaces"
+    input: #[
+        phrase: "vc vix    r hn"
+    ]
+    expected: "exercism"
+    function: "decode"
+    uuid: "39640287-30c6-4c8c-9bac-9d613d1a5674"
+] #[
+    description: "decode with no spaces"
+    input: #[
+        phrase: "zmlyhgzxovrhlugvmzhgvkkrmthglmv"
+    ]
+    expected: "anobstacleisoftenasteppingstone"
+    function: "decode"
+    uuid: "b34edf13-34c0-49b5-aa21-0768928000d5"
+]]
+
+
+foreach c-case canonical-cases [
+	case-code: reduce [
+		'expect c-case/expected compose [
+			(to word! c-case/function) (values-of c-case/input)
+		]
+	]
+
+	test c-case/description case-code
+]
+
+test-results/print

exercises/practice/atbash-cipher/atbash-cipher.red

@@ -0,0 +1,17 @@
+Red [
+	description: {"Atbash Cipher" exercise solution for exercism platform}
+	author: "" ; you can write your name here, in quotes
+]
+
+encode: function [
+	phrase
+] [
+	cause-error 'user 'message "You need to implement encode function."
+]
+
+decode: function [
+	phrase
+] [
+	cause-error 'user 'message "You need to implement decode function."
+]
+